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Full text of "Radio Electronics (October 1992)"

BUILD YOUR OWN HANDI-TALKIE! 



Build this 
high-efficiency 

HANDI-TALKIE 

«• ■ » . _ _ 



communications 



/ 



Combined 
with 



I 



i 



Build our 

REFLEX TESTER 

and find out just 
how fast you are! 

How to use the 

555 TIMER CHIP 

to build 
oscillator circuits 

Build a 
250-WATT 
POWER INVERTER 

to supply 120 volts AC 
from 12 volts DC! 

Use our 

PC-BASED 

TEST BENCH 

to identify and test 
digital IC's 





mm 



mm 


gxgMmm 


sst 


.-co." 








/ V 


$2.95 U.S. 
$3.75 CAN 


■V-.i4;1iKW:\H,' 


T PUBLIC AT tON 








> 




mxxxxx CAR-RT SORT ** CRO: 
75D45SHRR5165MD93 ID 2t 

NOU 9 




FLUKE AND PHILIPS - THE GLOBAL ALLIANCE IN TEST & MEASUREMENT 



FLUKI 




PHILIPS 



Introducing SCOPEMETER 



There's More Than One Reason to Reach for It. 

In fact, there's every reason to reach for ScopeMeter.'" Because only ScopeMeter 
combines the expertise of Fluke and Philips to bring yoj a dual-channel digital scope 
along with everything you've come to expect from Fluke digital multimeters. 

The result: an integrated scope-and-multimeter that lets you see a waveform and 
digital meter display at the same time from the same input. Or switch between 
dedicated high-performance Scope and Meter functions with the touch of a 
key. That makes it faster and easier than ever to capture, store and analyze 
precisely what you're looking for. At a price that looks good, too. 
To get your hands on a ScopeMeter, contact your Fluke sales office or your nearest 
Fluke distributor. For more product information, call 1-80Q-44-FLUKE. 

SCOPEMETER. Now there's only one to reach for. Simply Easy. 




Built to Take It. 

• Completely sealed against water, 
dust and contaminants. 
EMI protected and measures 
up to 600 volts rms. 
• Rugged construction with 
shock- resistant holster. 
■ Three-year warranty 
from Fluke. 



Double Duty. 



> 50 MHz digital storage scope and 
3000-couint digital multimeter in 
one held held package. 
• Precision Min Max Record and 
40 ns Glitch Capture make it easy 
to troubleshoct intermittent failures. 
* Simultaneous waveform and digital 
display on a backlit screen you can 
read across the room. 



S^g^cJLislFnEe 



Sample Hate 



Mullifflflsr Display 



True RMS Uslfs 



Diod* T«l 



ConMnjiiy Seflper 



" ma D ■*•% ?" 



Veils/Division 



2iri \2 De ay or 
Prc-Tfi-po&r 



Special Multimeter 
Modes 



Oscilloscope 
Cursors 



Glitch; Capture 



Waveform 
Processing 



Wave 1 rm Memory 



Sel .";: yemof^ 




* Intuitive front panel layout for 
simple, straightforward operation. 

* Pop-up menus and five function 
keys for easy control. 

* Autoset automatically sets voltage 
time and trigger functions. 

•Safety-designed SNC connectors 
and probes simplify floating 
measurements. 



FLUKE 90 SERIES SCOPEMETER SELECTION GUIDE 



Waveform 



Signal Generator 
Qutpul 



Dpr:cailv isolated 
RS-232-C Interface 



FLUKE 37 



$1735 



FLUKE 35 



SU95 



50 MH: Dual Channel 



35 Mcflasamptes»5ecQr-d 



AuiomatiL-jhy sals village Time and Trigg.*j 



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AC QT AC + OC up 1Q 6Q3V H70QV Pk-Pkl 



up to 2 ev 



TO -n&i'drj to 60 secJdiv 



■ fjfi m :- IQOVrtft 



B t N u mm r d1 Cycles . Events. Tame, 
or Zoom Mode 



Mm Max Average Hecuid. Relieve USfo), 
rJGnv dBV. rJBW. Audio Watts. % Scale, 

Frequency, Smooihinfi," Change Alert ' 



i? Measurements. 

!■ E P J > i- b "Li ■S , " ECi^Jlv 



Average. Variable Persistence. 
Min Max Record 



Sioreand Recall fl Wavelorms 



Store and Recall 10, 
Fro nt Pa-nel. Sd-Upa 



Add. Subtract.. 
Ntulliply. invert, 
filter or Integrate 

Waveforms 



S inswap or 
Square-wave 



Voltage Or 
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Full Operai ion by 
Remote Control 
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Serial 



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Goes Wherever You Go. 

■ Runs on rechargeable NiCatf Batteries, 
standard C-cells or the included line 
voltage adapter/battery charger. 

■ Adjustable lilt-stand/hanger. 

■ Compatible with a wide range of 
Fluke multimeter accessories. 

31992 John Fluke Mlfl Co Int U No. W33< 

FLUKE 



CIRCLE 121 OH FREE INFORMATION CARD 




October 1992 Bx°m 



Vol. 63 No. 10 



35 HANDI-TALKIE 

Use this efficient mini FM transceiver for business or amateur 

communications, 

Don Wray 

43 REFLEX TIMER 

Find out just how fast your reflexes are! 
Dan Kennedy 

61 DIFFERENTIAL PROBE 

Make safe measurements in ungrounded systems. 
Walter Dorfman 



47 PC-BASED TEST BENCH 

Build the T1003 digital logic IC tester. 
Steve Wolfe 

75 250-WATT POWER INVERTER 

Use it to power small appliances from your car. 
James Melton 



55 NOT WORKING TO NETWORKING 

Case histories of some problem LAN's. 
Gary McClellan 

69 THE 555: A VERSATILE OSCILLATOR 

Learn to use the 555 IC in circuits that wail, warble, and honk! 
Ray M. Marston 



79 HARDWARE HACKER 

Histograph equalization. 
Don Lancaster 

88 DRAWING BOARD 

Video scrambling. 
Robert Grossblatt 

97 COMPUTER 
CONNECTIONS 

Miniature multimedia. 
Jeff Holtzman 



8 VIDEO NEWS 

What's new in this fast- 
changing field. 
David Lachenbruch 

16 EQUIPMENT REPORT 

Computer monitor checker. 

78 AUDIO UPDATE 

Syndicated reviewers, AM 
stereo, and consumer fraud. 
Larry Klein 



BUILD THIS 

REFLEX TIMER 


















PAGE 43 




PAGE 75 



106 Advertising and Sales 
Offices 

106 Advertising Index 

97 Buyer's Market 

4 Editorial 

14 Letters 

32 New Lit 

22 New Products 

12 Q&A 

6 What's News 




ft! 



I 



S 

1 

hi 




Whether you need a handheld 
transceiver for business or for ama- 
teur-radio — or just want to build one 
forthefunofit — ourHandi-Talkiehas 
a lot to recommend tt. The small, 
light-weight transceiver is powerful 
and efficient, offers narrow- band 
FM modulation and can be designed 
to operate anywhere from 27 to 32 
MHz — and even up to 60 MHz with 
minor parts changes! That config- 
uration allows the Handi-Talkie to 
work both the six- and ten-meter 
amateur-radio bands. Thanks to the 
use of surface mount technology, the 
whole device, including a re- 
chargeable nickel-cadmium battery 
pack, is housed in a case less than 
six inches long, Turn to page 35 for 
all the details! 



THE NOVEMBER ISSUE 

GOES ON SALE 

OCTOBER 6. 

PHOTO SOUND STROBE 

This project brings the worlds of electronics and photography 

together to capture exciting, astounding images on film. 

SOLAR EVENT MONITOR 

Keep track of magnetic-field anomalies that can disrupt — or en- 
hance—communications. 

CIRCUIT COOKBOOK 

A variety of astable- and monostabte multivibrator circuits based 
on the 555 timer. 

AUTOMOTIVE POWER RELAY 

This "smart" switch is perfect for controlling such high-current 

devices as auxiliary lights and high-power audio amplifiers. 

As a service to readers. ELECTRONICS NOW publishes available plans Of information relating to newsworthy products, 
techniques and scientific end technological developments. Because of possible variances in the quality and condition of 
materials and workmanship used by readers. ELECTRONICS NOW disclaims any responsibility for the safe end proper 
functioning of reader-built projects baaed upon or from plans or information published in this magazine. 

Since some of the equipment and circuitry described in ELECTRONICS NOW may relate to or be covered by U.S. patents. 
ELECTRONICS NCW disclaims any liability for the infringement of such patents by the making, using, or selling of any such 
equipment or circuitry, and suggests that anyone interested in such projects consult a patent attorney. 

ELECTRONICS NOW. USSN 0033-7B62) October 1992. Published monthly by Gemsback Publications, Inc.. 500-B Bi County 
Boulevard, Farmingdale, NY 11735. Second-Class Postage paid at Farrningdele, NY and additional mailing offices. Second- 
Class mail registration No. R125166280. authorized at Toronto. Canada. One-year subscription rate U.S.A and possessions 
$19.97, Canada $27.79 (includes G.S.T. Canadian Goods and Services Tax Registration No. R 1 251 66280), all other countries 
$28.97. All subscription orders payable In USA. funds only, via international postal money order Of check drawn on a U.S.A. 
bank. Single copies $2-95- '£ 1992 by Gemsback Publications, Inc. All rights reserved. Printed in U.S.A. 

POSTMASTER : Plea se se n d address changes to E LECTRON ICS NOW, Su bscription De pt . Bo x 5 5 1 1 5 . Boulder. CO 8032 1 - 5 1 1 5 

A stamped self- addressed envelope must accompany all submitted manuscripts and/or artwork or photographs if their return is 
desired should they be rejected. We disclaim any responsibility for the loss or damage of manuscripts and/or artwork or 
photographs while in our possession or otherwise. 



Electronic, 



Hugo G e rn s bac k (1 884- 1 967) fo n n d . 

Larry Stockier, EHF, CET, 
editor-in-chief and publisher 

EDITORIAL DEPARTMENT 
Brian C. Fen ton, editor 
Marc Spiwak, associate editor 
Neil Sclater, associate editor 
Teri Scaduto, assistant editor 
Jeffrey K. Hottzman 

computer editor 
Robert Grossblatt, circuits edito 
Larry Klein, audio editor 
David Lachenbruch 

contributing editor 
Don Lancaster 

contributing editor 
Kathy Terenzi. editorial assistant 

ART DEPARTMENT 
Andre Duzant, art director 
Injae Lee, illustrator 
Russell C, Truelson, illustrator 

PRODUCTION DEPARTMENT 
Ruby M, Y», production director 
Karen S. Brown 

advertising production 
Marcella Amoroso 

production assistant 
Lisa Rachowitz 

editorial production 

CIRCULATION DEPARTMENT 
Jacqueline P. Cheeseboro 

circulation director 
Wendy Alanko 

ctrcu lati on analyst 
Theresa Lombards 

circulation assistant 
Michele Torrillo 

reprint bookstore 

Typography by Mates Graphics 
Cover photo by Diversified Photo 
Services 

Electronics Now is indexed 
Applied Science & Technology Inc 
end Readers Guide to Periodical Li. 
store, Academic Abstracts, a 
Magazine Article Summaries. 
Microfilm & Microfiche editions . 
available. Contact circulation depi 
ment for details. 

Advertising Sales Offices list 
on page 102. 

Electronics Now Executive and 

Administrative Offices 

1-516 293 3000. 
Subscriber Customer Service: 

1-800-288-0652. 
Order Entry for New Subscribers: 

1-800-999-7139. 



Audit Bureau 

of Circulations 

Member 




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v For Electronics 



Custom Molded Carrying Case 
folds into briefcase size 



Function Generator 
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Holds Digital Multimeter 
PRQTQ-METEH® 4000 

(optional) 



Denounce Push-Buttons 

Two BNC Connectors for 

oscilloscopes and counters ' 




Compartment for text books 
manuals and/or wire jumper 
(optional) 



Large Breadboard area hoi 
24 ICs.,.2,500 tie points 



Triple Power Supply.+SV Hxi 
plus two variable 5-1 5V 



8 TTL Logic Probe Indicator. 



Audio Speaker 



M& 




Here's PB-503-C. It has every feature that our famous 
PB-503 offers, but we added one more, portability. 
Work on your projects at the office or school, take it 
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to take their lab with them. Instrumentation, including 
a function generator with continuously variable sine, 
square, triangle wave forms and TTL pulses. 
Breadboards with 8 logic probe circuits. And a Triple 



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guarantee on all breadboarding sockets! And, becc 
it's portable you will always have everything you r 
right in front of you! PB-503-C. one super tesi st< 
for under $350! Order yours today!! 





FOR MORE INFORMATION GLOBAL 

CALL 1 -800-572-1 028 SPECIALTIES' 



G total Specialties ', 70 Fulton Terrace, New Haver>, CT 065 12 
Tele: 203-624*31 03/Fax: 2O3-4&3»0060 - C1»0, Inierple* Etoclrcflics 
All Global Specialties' freadbcurding products are made in the U.S. A 
Proio-Baard is a registered Iradamark at Global Specialise?.- A033 



CIRCLE 182 ON FREE INFORMATION CARD 



EDITORIAL 



NOW'S THE TIME 



Now, according to Webster's New World Dictionary, means "at the 
present time; at this moment." Electronics Now is just what its 
name implies: a compilation of what is happening in electronics at 
this moment! 

Electronics Now brings you the latest news, the newest products, 
the most useful training, the most exciting projects, the newest 
how-to information. We help you learn how it works, how to keep it 
working, and, of course, how to make your own. We even show 
you what may happen tomorrow. 

Above all else, we remain your electronics magazine. We know 
that the great majority (89%) of you earn your living in electronics. 
But you are the engineers and technicians to whom being an 
electronics professional is more than just a job. In your spare 
time — your leisure time — your personal time — you still want to 
know and learn more about electronics. 

You want to know how Caller ID works. You want to know how 
digital audio tape compares to digital compact cassettes. You need 
to know about cellular telephone services and the personal 
communication networks of tomorrow. You need to know what 
microprocessor your next computer will have. You have to know 
what the next generation IC's will be like. 

Bringing you information on those and other subjects is our forte. 
We work and strive to stay on top, to learn, to explore, and follow 
late-breaking developments in electronics. And we do it now! 
That's where our new name — Electronics Now — comes from. 
That's what we bring to you — today and tomorrow — 
Electronics Now! 



Stay with us as we evolve and grow to meet the ever growing 
challenge of the electronics revolution. Stay with us as we continue 
our quest for the most exciting, most revolutionary and most 
daring developments of today and tomorrow. Become, through our 
pages, a part of the most important and influential segment of our 
modern world. Come with us as we become Electronics Now. 




>&U*idt*' 



Larry Steckler, EHF/CET 
Editor-in-Chief and Publisher 



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CIRCLE 183 ON FREE INFORMATION CARD 



WHAT S NEWS 



A review of the latest happenings in electronics. 



64-megabyte memory chip 

A computer memory chip jointly 
developed by engineers at IBM (Es- 
sex Junction, VT) and Siemens can 
store more than 64-million bits of 
data — four times the capacity of the 
most advanced memory chip in 
computers today. 

The new dynamic random access 
memory (DRAM) chip can store the 
equivalent of about 6000 pages of 
double-spaced typewritten text, 
and can "read" more than 64-million 
bits on the chip in a fraction of a 
second. The chip measures 
10.7mm by 18.1mm (approximately 
3 /s-)nch by %-inch). 

The chip was developed with an 
advanced CMOS technology pro- 
cess. Its smallest conductive traces 
are 0.4 micrometers wide, about 
one two-hundredth of the thickness 
of a human hair. The transistor gate 
insulator, a nonconducting layer that 
separates conducting layers on the 
chip.measures only 10 nanometers 
in thickness. 

The electrical charges that make 
up each bit of information are stored 
in a buried-plate trench cell. A con- 



ductive region in this cell is diffused 
from the bottom part of the trench 
into the substrate. That region 
serves as the common buried-plate 
contact to all the cells. The trench's 
sidewalls are covered with an in- 
sulating material, and the trench is 
then filled with conductive silicon. 
Information is stored in the material 
inside the trench. 

The entire trench area occupies 
only 1.5 square micrometers. The 
cell is so small that nearly one mil- 
lion of them can fit on the head of a 
pin. 

The 64-megabit chip, which oper- 
ates from a single 3. 3- volt power 
supply, has borderless contacts 
that eliminate the necessity for 
providing a border around the metal 
that forms electrical contacts to 
specific areas of the chip.Bor- 
deriess contacts reduce the area of 
the chip. 

IBM and Siemens began their 
joint development on the chip in 
January 1990. Their goal is to have 
the chip ready for mass production 
by the middle of the decade. 

In July IBM announced that it is 




A SERIES OF MEMORY CELLS IN THE IBM/SIEMENS 64-millIon-bit computer memory 
chip as seen with an electron microscope. 



joining with Siemens and Toshib; 
develop 256-megabit DRAMS. 

Faster silicon circuits 

Westinghouse Electr 
Corp. (Pitts burgh, PA) has recek 
a government contract to deve 
silicon transistors that operate 
higher speeds than today's devic 
The new technology is expected 
extend the use of low-cost silic 
substrates into the higher-freqw 
cy regions of radar, cellular te 
phones, digital radio, and ultra-hii 
speed computing. 

The $624,000 U.S. Navy F 
search Laboratory contract, wh 
extends through the end of 19! 
supports further development 
the silicon-on-insulator tec 
nology — called Microx. The tei 
nology will be used for applicatic 
in which both microwave radio e 
digital functions are built into 1 
same monolithic chip. 

Experimental microelectroi 
chips fabricated from Microx hj 
operated at the microwave frequi 
cies of 30 GHZ and they are i 
pected to achieve 40 Gh 
smoothing the way to a new gene 
tion of low-cost, mixed function F 
digital silicon monolithic circu 
whose speeds are comparable 
those attained by gallium-arsen 
devices. Westinghouse believ 
these to be the highest frequenc 
ever reported for linear MOS silic 
transistors. 

The key innovations are ion-i 
planted oxide layers produced wi 
in a high-resistivity substrate tl 
resembles an insulator, combin 
with several advanced fabricati 
techniques. According to Mich 
C. Driver, manager of mici 
electronics at the Westinghou 
Science & Technology Center, t 
crox can realize at least 10 decib 
of power gain at 1 GHz. This peri 
mance.he said, coupled with t 
low cost typical of silicon M( 
technology, opens up a broad rar. 
of applications. P 



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VIDEO NEW5 



What's new in the fast-changing video industry. 



DAVID LACHENBRUCH 



• Digital TV gains. There has 
been a notable shift in the direction 
of the world HDTV winds in the last 
few months. Despite the fact that 
both Europe and Japan are theo- 
retically committed to analog sys- 
tems, the United States suddenly 
has assumed unquestioned lead- 
ership in the HDTV field. Progress 
here in digital HDTV — and proof 
that digital systems actually can 
work — has sent shock waves 
through Japanese and European 
television circles. Now, for the first 
time, engineers in both regions are 
looking seriously at digital systems, 
and predicting that their countries 
"ultimately" will go digital. 

Japan. In Japan, where the ana- 
log MUSE Hi-Vision system is actu- 
ally being broadcast by satellite for 
eight hours daily, engineers are be- 
ginning to forecast an eventual 
switch over to a digital compressed 
system. Japan's commercial broad- 
casters have always been slightly ill 
at ease over the publicly supported, 
non-commercial NHK network's es- 
pousal of Hi-Vision, but for direct 
satellite broadcast only. The Hi-Vi- 
sion system is now almost 20 years 
old and it ignores some of the newer 
technologies employed in other 
HDTV systems. Prices of HDTV re- 
ceivers have been coming down — 
but from the rarefied level of 
$30,000 to the still high $10,000— 
and sales have been extremely 
slow. 

One manufacturer's view. Digital 
HDTV is "quite likely to be the wave 
of the future" in Japan, said Hiroyuki 
Mizuno in the keynote address to 
the Internationa] Conference on 
Consumer Electronics CICCE) in 
June, the annual meeting of Amer- 
ica's consumer-electronics engi- 
neers in Chicago. The statement is 
significant because Mizuno is ex- 
ecutive vice president of Mat- 
sushita Electric, the world's largest 
producer of consumer electronics. 
Mizuno called the analog Hi-Vision 



system a "bird in the hand," giving 
the Japanese people and TV set 
manufacturers experience in high 
definition. 

But Mizuno said digital HDTV will 
"inevitably fuse" the TV and the 
computer, making TV a "digital mul- 
timedia broadcast station which can 
process, store, create, and transmit 
video images." Conceding that "we 
are experiencing temporary tech- 
nical difficulties" in supplying prac- 
tically priced HDTV receivers and 
VCR's in Japan, he said that these 
problems eventually will be solved, 
but he didn't say whether the solu- 
tion would be digital or analog. 

Europe. Europe's Eureka project, 
designed to develop an HDTV sys- 
tem different from Japan's, envi- 
sions a two-stage move to HDTV. 
The first stage would be broadcast- 
ing in a widescreen improved sys- 
tem called D2-MAC. followed by a 
move to HD-MAC, a high-definition 
system. However, neither system is 
compatible with the existing PAL 
and SECAM broadcasts in Europe, 
and both systems were designed 
for direct satellite transmission. Eu- 
rope's satellite broadcasters are 
having financial difficulties, and gen- 
erally have refused to adopt MAC 
broadcasting, preferring to continue 
to use PAL, which is compatible 
with TV sets there. Despite tremen- 
dous pressure by TV manufacturers 
and proposals to issue large gov- 
ernment subsidies for a 
changeover, MAC's adoption has 
been sluggish. Europe's broadcast 
authorities, with a nervous eye on 
the HDTV research in the United 
States, have been quietly working 
on digital systems for Europe. With 
the MAC structure coming under 
increasing criticism (for instance, it 
ignores terrestrial broadcasting, 
which produces 90% of the broad- 
cast ad revenues in Europe and has 
more than 90% of the audience), 
demands for a change to digital ter- 
restrial HDTV have been sounded 



more frequently in recent mont 
and research toward a digital s 
tern has come out of the closet ; 
is being discussed openly. 

Just a few years ago, it was po 
lar to say that the United States \ 
far behind Japan and Europe 
HDTV. Today it is accepted that < 
ital broadcasting is the wave of 
future, and that the United State 
in the vanguard. Officially, Jaf 
might be very proud that it was f 
and that its system has been un< 
development for 20 years — but t 
makes it a 20-year-old system, 
contrast to America's up-to-tl 
minute approach to HDTV. 

HDTV set availability. When 
HDTV receivers be widely availa 
in the United States? The Advanc 
Television Advisory Committ 
CATAC) to the FCC recently set i 
to get the answer, so it sent qu 
tionnaires to all major TV manuf 
turers serving the United Stat 
market — a total of 14. It received 
replies. ATAC specifically asked 
"time of general availability to o 
sumers from multiple sources' 
not for the time of shipment of "c 
set per showroom." 

The replies indicated that HD 
sets would be plentiful 2'/2 to thi 
years after the FCC approver 
transmission system. That even' 
tentatively scheduled for late 195 
However, some respondents repl 
that sets could be available soot 
if manufacturers take a chance e 
start developing them as soon 
the advisory committee makes 
recommendation to the FCC. Tl 
is expected in February 1993. A 
the survey showed that HDTV s; 
tern proponents that also manuf; 
ture TV sets — Philips, Thoms< 
and Zenith — might have a six- 
nine-month advantage over th 
competitors. Other manufactun 
that develop their own IC's mi< 
have a three-month advantage o* 
those that buy chips from othe 
the survey revealed. R 



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Q&A 



Write to Q&A, Electronics Now, 500-B Bi-County Blvd., Farmingdale, NY 11735 



LOCAL BUS 

I've been hearing a lot about 
local-bus computers, but I can't 
seem to find a clear definition of 
exactly what they are and why 
they're supposed to be so ter- 
rific. Several computers in the 
mail-order advertisements tout 
the feature, and each one that 
does is quite a bit more expen- 
sive than similar ones without a 
local bus. Can you explain to me 
in simple terms what a local bus 
is, and whether it's worth the ex- 
tra money? — R Geeben, Ana- 
wana, NY 

All the peripheral cards that plug 
into your computer, such as the vid- 
eo card and others, get their basic 
clock speed from a single pin on the 
bus. The clock speed comes from 



the master oscillator on the mother- 
board, which is usually the one 
that's clocking the microprocessor. 

For reasons buried deep in the 
corporate vaults at IBM, the bus 
clock was usually limited to a max- 
imum of 6 or 8 MHz — that was the 
speed of the last of the original AT's 
that had a standard bus. With the 
introduction of the PS/2 series of 
computers, IBM abandoned the old 
standard bus and began using the 
MicroChannel Bus — a different 
thing altogether. 

That change left the compatible 
and clone manufacturers in a bit of a 
quandary since they no longer had a 
developing standard from IBM. The 
original AT had a 16-bit bus because 
that was the internal bus size of the 
80286 (the last microprocessor 



IBM used in the AT). IC's such a 
386 and 486 are 32-bit m 
processors, but IBM's new 3 
MicroChannel Bus was a propri 
bus. The result was a lack < 
accepted standard for a 32-bit 

With the exception of IBM, 
puter manufacturers have rec 
agreed on the EISA CExtende 
dustry Standard Architecture 
bit bus that has shown up in a 
newer PC-compatibles. The c 
sis of the local bus is similar. 

While some cards that pluc 
the slots at the back of the mc 
board have to run at speeds si 
than the microprocessor, a 
others are perfectly happy to r 
microprocessor speeds. A goc 
ample of this is the video ads 
which can easily be designed t 



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at speeds higher than those avail- 
able with the standard bus clocks. 

Along with the adoption of the 
EISA bus, the local bus is a system 
in which a separate bus is provided 
for certain peripheral cards that 
don't have to be limited to standard 
bus-clock speeds. The result is 
much faster operation, and for 
something such as video, the dif- 
ference is astounding. 

Deciding if something is worth 
spending money on is a personal 
decision, so I won't answer that part 
of your question. However, because 
this is a recent development, man- 
ufacturers are just starting to pro- 
duce local-bus peripherals so you 
might want to wait and see what 
develops over the next few months 
and whether a standard takes hold. 

AUDIO CROSSTALK 

I've been getting a lot of 
crosstalk between audio chan- 
nels and, after eliminating every 
other possibility, I've come to 
the conclusion that the signals 
are leaking through the power 
supply. There doesn't seem to 



be anything on the circuit 
boards to take care of the prob- 
lem so I guess I 'If have to do it 
myself. Could you tell me what 
the basic circuit setup is for 
power-supply decoupling? — A. 
MacDonnell, Mill Hill, NY 

tf you're sure that the power sup- 
ply is the source of your problem, 
and it turns out that you're right, you 
can consider yourself lucky be- 
cause it's easy to take care of. 

The basic design for power-sup- 
ply decoupling is shown in Fig. 2 
and, as you can see, there isn't 
much to it. You can get a lot more 
involved when you're dealing with 
very high frequencies, but because 
you're only concerned with audio 
stuff, the layout in Fig. 2 will be fine. 

The resistor values should be cal- 
culated by looking at the maximum 
current draw of the equipment and 
applying Ohm's law. Remember that 
the resistors will be carrying all the 
current needed by the circuit, so 
you should pay proper attention to 
their wattage as well. In general, as 
long as you're dealing only with line- 
level stuff, you can use quarter-watt 




FIG. 1— POWER-SUPPLY DECOUPLING 
CIRCUITRY. These circuits can get a lot 
more complicated, but for audio fre- 
quencies, this is more than enough. 

resistors and everything will be OK, 
Once you calculate the needed 
resistance (supply voltage/max- 
imum current), add another fifty per- 
cent to the value just to be on the 
safe side. Audio levels can vary all 
over the place, and if you're listen- 
ing to something with a really wide 
dynamic range, too low a value on 
the resistor will cause the signal to 
clip. 

There's nothing magical about the 
choice of the capacitor value either, 
and I've used everything from 10 to 
100 u.F without any noticeable dif- 
ference. You would think that the 
circuit would call for a non-polarized 
continued on page 15 






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LETTERS 



Write to Letters, Electronics Now, 500-B Bi-County Blvd., Farmingdale, NY 1173L 



i 

s 



Z 
S 

e 

tj 
jn 

HI 

14 



EQUIPMENT REPORT UPDATE 

Thank you for the wonderful 
Equipment Report on our Compu- 
Scope LITE IBM PC-based os- 
cilloscope (Electronics Now, 

August 1992). We wholeheartedly 
agree with you that "PC-based in- 
struments are the leading edge of 
growth for test and measurement." 
Gage has been a major contributor 
to the buildup of that industry for the 
past five years. 

In the same article, three valid 
criticisms were made by your re- 
viewer. Because those points have 
also been raised by some of our 
customers around the world, we 
have been working to solve the 
problems. In July 1992 we released 
a new software package called 
GageScope for our complete line of 
CompuScope cards. 

First, we have drastically im- 
proved the hardware installation 
procedure. We have rewritten the 
entire documentation and software 
supplied with the CompuScope 
LITE card with special emphasis on 
installation. The 112-page manual 
has a 15-page section on board in- 
stallation, full of examples and 
charts on how to configure a new 
I/O address even if the user does 
not know hexadecimal mathe- 
matics. 

Second, to improve the descrip- 
tion of the menus in the manual, we 
included a detailed description of 
each menu entry, as well as a 13- 
page tutorial that guides the user 
through the most often-used menu 
commands. 

Finally, to satisfy the needs of 
more sophisticated customers, we 
offer other products: CompuScope 
220, a 40-MHz card with up to 8 
megabytes of memory, and Com- 
puScope 250, which samples at 
100 MHz. Our products are being 
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as NASA, IBM, Honeywell, and 
Motorola, and hundreds of smaller 
less well known companies and indi- 
vidual customers. 



We think that, overall, your review 
was very positive about the impor- 
tance of PC-based instruments in 
general, and CompuScope LITE in 
particular. We are very excited 
about our coverage in Electronics 
Now. 

MUNEEB KHALID 
Vice President 
Gage Applied Sciences Inc. 
Montreal, Quebec, Canada 




SURFMAN DIODE REVERSAL 

An error appeared in our Surf- 
Man sound gernerator article 
(Electronics Now. August 
1 991 ), Diode D2 was incorrectly 
drawn reversed in the parts 
placement diagram, Fig. 2 on 
page 35. However, it is drawn 
correctly in the schematic, Fig. 
1 on page 34. 



IC SUBSTITUTION 

Mr. Caristi is to be congratulated 
for his article "Digital Altimeter" 
(Radio-Electronics. May 1992). 

There is one point that concerns 
me, however. IC3 gives a full-scale 
reading for a 100-millivolt input 
change (from 2.5 to 2.4 volts at pin 
30), which is an effective sensitivity 
of 20 feet per millivolt. My concern 
is the choice of the LM324 as IC1. 
While it is a very useful chip indeed, 
it does not exhibit low off-set drift 
with temperature. Prospective con- 
structors who think that shortcom- 
ing could be a problem might want 
to consider replacing the LM324 



with four devices such as C 
which have impressively lov. 
D.M. BRIDGEN 
Reading, Berks., U.K. 

CLASSIC VIDEO AMF 
RE-REVISITED 

I enjoyed seeing my . 
"Classic Video Amps Rev 
published in the June issue 
dio-Electronics. Thanks! 

However, in the editing t 
some errors crept in. The fi 
occurs in the second paragi 
page 60. The wording impli 
the 733 is the better choice 
in filters; that's not so. The 5 
vides the greatest attenue 
the unwanted signal. I tried 
that the the 592 will provic 
voltage gain with a high imp 
across the gain control pin 
and G1B), the desired desigr 
tive at those points for tho 
nals. In fact, the 733 would b 
choice For this application b 
it provide a minimum 20-c 
oretical gain for the unwante 
signals. 

Paragraph four implies t 
through D4 are forward bias 
odes D1 and D2 are reversed 
and D3 and D4 are not biast 
or only forward biased wl 
overvoltage signal is appliec 
circuit. That is necessary fc 
protection. 

Also on page 60, Fig, 7 sh 
with a shorting bar across t 
wipers. That connection is 
rect. There should only be s 
lated mechanical connectior 

On page 61. Q1 in Fig. 9 
be a PNP device and it she 
labeled 2N4959/2N3906 
than 2N4959/2N3904. Alsc 
9. 03 should be a PNP devii 
ure 8 can be used to illustn 
proper configuration. 

Overall, the article fulfills 
jective of stating that both t 
and 733 video amplifiers c 
recommended for new desk 
EDGARDO PEREZ 



O&A 



continued Jrom page 13 



capacitor, but my experience is that 
polarized capacitors work just as 
well. Remember that you're not 
dealing with high current and volt- 
age levels here, and that gives you a 
considerable amount of leeway. 

LINE-LEVEL DIFFERENCE 

I've noticed that there's a con- 
siderable difference in the audio 
level that comes out of my CD, 
tuner, cassette player, and other 
equipment. When I switch my 
amplifier from one source to an- 
other I can often hear a dramatic 
difference in the levels. Is there 
some way to buffer those sig- 
nals between the equipment and 
the inputs to my power amp so 
the levels presented to the amp 
are all the same? — D. Gould, 
Michigan City, IN 

You can call them buffers, but as 
far as I can see, what you really need 
is a preamp on each line so you can 
adjust the level from each device 
before it gets to the power-amp in- 
puts, A lot of the consumer audio 
equipment on the market really 
cheaps out when it comes to the 
output level. The cassette and CD 
players on my shelf, for example, 
are top of the line units, but neither 
of them has a convenient front panel 
control for adjusting the output 
level. 

There are really three ways you 
can handle this problem. The first, 
and easiest, is simply to drop all the 
levels to that of the lowest one with 
simple resistor pads. Once you've 
done that, you can set the power- 
amp level and not have to change it 
every time you switch from one 
source to another. 

The second way to deal with this 
involves a bit more work, but is not 
really all that difficult. Although 
there's no front-panel control for the 
output level, you can bet your new 
pair of white tennis shoes that 
there's a trimmer somewhere inside 
each of the players that sets the 
output level. Just get yourself a 
screwdriver, take the cover off, and 
start exploring. It's a good idea to 
have the service manual around 



when you do this, but most of the 
consumer audio stuff I've seen has 
the function of the trimmer 
silkscreened on the printed-circuit 
board. 

The last approach to the problem 
is to build a bunch of preamps with 
line-level inputs and outputs. You 
can put them between the equip- 
ment and the power amp and adjust 
the levels that way. I'd do that only 
as a last resort. It's a lot more work 



because you'll need two preamps 
for each piece of equipment (as- 
suming, of course, that you're deal- 
ing with stereo). Besides the extra 
work. I've never been convinced 
that it's a good thing to have more 
electronics on the line than the bare 
minimum required. That's because 
any extra electronics is a potential 
noise generator, and also a potential 
entryway for externally produced 
noise. R-E 




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The Checker Computer Monitor Tester 




Computer monitors and start- 
dards have certainly 
changed dramatically in the 
last decade. We've moved from 
composite video monitors through 
the MDA. CGA, HGC (Hercules), 
EGA, VGA, and SVGA standards. 
And there are yet other standards in 



use, and more in the wings. One 
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is that computers monitors even- 
tually need service. 

The Checker, a new product from 
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was designed with that in mind, 
though The Checker is a rather s 
pie service tool, it can make thir 
easier for any monitor repair tecf 
cian. or for anyone who manages 
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an office environment. 

The Checker is packaged in a r 
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serves as the power switch as v 
as an output-mode control. Two \ 
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adapter is also provided to run ' 
unit from the AC lines. 

The Checker provides three c 



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put modes: CGA Ccofor graphics 
adapter), EGA (enhanced graphics 
adapter) and VGA (video graphics 
array). Only standard VGA resolu- 
tion (640x480) is supported. 

Using the Checker is straightfor- 
ward: Turn the unit on, set the prop- 
er mode, and connect the monitor. 
In the CGA mode, you'll see two 
sets of color bars: high-intensity on 
the top half of the screen, low-inten- 
sity on the bottom. In EGA mode, 
three sets of color bars are pre- 
sented. In VGA mode, the Checker 
generates a single set of eight color 
bars. 

Even though the Checker is 
rather simple, we can come up with 
many uses for it. Around the Elec- 
tronics Now offices, for example, 
we could use it for quick checks of 
monitor problems. When someone 
reports a monitor problem, the usu- 
al first check is to swap out the 
suspect monitor with one that is 
known to be good. (Of course if its 
the graphics card that is bad, then 
another swap is required.) That first 
step is basic, simple troubleshoot- 
ing to narrow down the problem. 



Unfortunately, that simple meth- 
od has its own problems. First is the 
time and trouble to move heavy 
monitors around. Second is the lim- 
ited space that is available at the 
computer — there's usually not 
enough room to work conveniently. 
The handheld Checker weighs less 
than a pound, and permits a monitor 
check to be done in just a minute or 
two. 

For anyone who maintains an in- 
ventory of computer monitors, the 
Checker could also come in handy. 
Is the monitor that is to be installed 
for that new employee working? The 
Checker lets you find out before you 
haul a non-working monitor over to 
the installation site. 

The Checker also has a place in 
professional service shops. It can 
be used, for example, to "burn in" a 
monitor without tying up special 
test equipment or a computer (with, 
of course, the correct graphics card 
installed.) When a customer comes 
in to pick up his monitor, the Check- 
er makes an ideal way to demon- 
strate that the repair was suc- 
cessful and that the monitor is now 



working properly. It can also be used 
as an aid in setting vertical and hori- 
zontal size controls correctly. 

The Checker does not support 
Hercules-type monochrome 
monitors. That's an unfortunate 
oversight in our opinion. Although 
such monitors are not popular sell- 
ers these days, there are an awful 
lot of older units in circulation, and 
older equipment is more likely to 
develop problems. We would also 
have preferred to see an SVGA 
(super VGA) mode and test pat- 
terns more useful than the non- 
standard color bars that are pro- 
vided. 

With a price of $229.95, the 
Checker is far too expensive for ca- 
sual use. However, the speed and 
ease with which the Checker can 
provide a go/no-go indication would 
be welcome by anyone who spends 
a lot of time checking a lot of 
monitors. When you consider the 
amount of time that the device could 
potentially save, and the headaches 
it could help prevent, the Checker 
could prove to be a worthwhile pur- 
chase. R-E 




The World is Talking! 



Shortwave 

Listening 
Guidebook 

by Harry Helms 

Here's your guide 
to getting the most 
from a shortwave 
radio! In clear, 
nontechnical language, Hany 
explains how, when, and where to listen 
in. Its 320 heavily -illustrated pages are 
packed with advice on: 

• antennas 

* selecting the right radio 

* accessories 

• reception techniques 

Learn how to hear the BBC, Radio 
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spies and "pirate radio stations! Includes 
hundreds of station frequencies and the 
times you can hear them. 

Only $16.95 at radio equipment dealers, 
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compatible computers. 

You'll use your Ultra-X 
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LOGIC PROBE. Beckman In- 
dustrial's LP50 is an inex- 
pensive, small 50-MHz 
logic probe that can detect 
pulses as short as 10 
nanoseconds. The pen-siz- 
ed logic probe is intended 
for troubleshooting high- 
speed, microprocessor- 
controlled circuits and the 
detection of extremely fast 
pulses. According to Beck- 
man, the probe measures 
TTL, DTL, and RTL logic 
levels at frequencies up to 
50 MHz. 

The LP50 is powered 
from the circuit under test 
through an alligator clip 
that provides a secure con- 
nection to circuit ground. 
The mini-hook clips onto 
the circuit's positive volt- 
age points. When the 
probe tip is touched to the 




CIRCLE 16 ON FREE 
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signal test point, the probe 
simultaneously lights an d 
LED and generates a tone 
to make it easy for the user 
to understand what is hap- 
pening at the test point. 



The LP50 logic probe is 
priced at $45. — Beckman 
Industrial Corporation, 3883 
Ruffin Road, San Diego, CA 
92123-1898; Phone: 
619-495-3218. 



CABLE/TV SIGNAL-LEVEL 
METER. Leader Instru- 
ments' Model 951 RF sig- 
nal-level meter is intended 
for broadcast and cable TV 
measurements. It features 
auto-channel search to 
measure the store level 
data for up to 32 channels. 
The LED bargraph display 
is arranged in groups of 
eight channels and it pro- 
vides readout of the se- 
lected channel in dBmV or 
other user-selectable engi- 
neering units. 

Autoranging is featured 
but manual ranging can be 
selected. The Model 951 
also operates in the single- 
channel mode with a com- 
bination bargraph and dig- 
ital readout of level in 
selected engineering units. 
The meter's operation can 



be programmed for video 
or sound-carrier levels of 
channels selected by the 
operator. 




CIRCLE 17 ON FREE 
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Frequency data for the 
USA and other countries 
are stored. Up to 32 chan- 
nel readings can be stored. 
DC and AC voltages on the 
cable can also be read. The 
portable instrument mea- 
sures 8 3 /a x 4 % X 7 %- 
inches and it weighs IOV2 
pounds. Powered by D 



cells, it has an auto-off fea- 
ture that extends operating 
time. 

The Model 951 CATV/ 
TV signal level meter has a 
price of $1 695.— Leader In- 
strument Corporation. 380 
Oser Avenue, Hauppauge, 
NY 11788: Phone: 
1-800-645-5104 or 
51 6-231 -6900 in New York. 

KEYBOARD-CONTROLLED 
POWER SUPPLIES. Kepcos 
DPS Series of keyboard- 
controlled power supplies 
provide 75 watts of DC 
power in four ranges from 
to125 volts. Eachpower 
supply is controlled by a 
keypad that commands a 
built-in microprocessor to 
set voltage, current limit, 
range, over voltage protec- 
tion COVP), displays, and 



over-current protection. 
Remote talk-listen c 
teol can be exercised v 
an RS-232C connect 
that can be addressee 
Basic and most comrr 
computer languages. K 
pad slew controls per 
continuous adjustment 
voltage up and down 
fine tuning while the out 
is enabled. Separate L 
displays provide volte 
and current readout. 




CIRCLE 18 ON FREE 

INFORMATION CARD 

DSP power supplies t 
priced at $429.— Kept 
Inc.. 131-38 Sanford A 
nue. Flushing, NY 113! 
Phone: 718-461-7000; R 
718-767-1102. 

MULTIFUNCTION 0UTL 
TESTER. Polytronics Su 
Test Pro Multifunction O 
let Tester is said to be al 
to provide a higher level 
assurance of power de 
ery than conventional vc 
age meters in situatio 
where the power source 
critical. 

The meter test for c 
rent capability by creatine 
12-ampere load on the lir 
Applied in short interva 
the 12-ampere power dr; 
can reveal the presence 
a faulty circuit breaker o 
sag in power delive 
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poor contacts or impror; 
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Order your copy direct or 
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D YES PLEASE SEND ME THE FOLLOWING 
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QWCKCrvss-* software runs in MS-DOS on any IBM PC or compatible with 640K of 

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CIRCLE 19 ON FREE 
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The SureTest Pro tests 
seven outlet parameters: 
miswires and incorrect wir- 
ing, proper voltage and cur- 
rent capability, ground 
faults (6-milliampere trip 
current), ground/neutral 
voltage latch, ground/neu- 
tral short, and high ground 
impedance. The unit is 
plugged into an outlet, and 
LED indicators provide go/ 
no-go readouts for all 
tests. 

The SureTest Pro multi- 
function outlet tester (Part 
No. 413B200) is priced at 
$179. — Jensen Tools Inc., 
7815 South 46th Street, 
Phoenix, AZ 85044; 
Phone: 602-968-6231. 

HEAVY-DUTY CABLE TEST 
CUP. ITT Pomona's Model 
5784 test clip permits the 
probing of insulated wires 
or cables without stripping 
the insulation. It is intended 
for use in laboratories, auto 
service shops and factory 
maintenance facilities. The 
clip is said to assure 
positive electrical contact 
and true readings, and it 
provides safe high-voltage 
lead testing with operator 
protection of up to 1000 
volts AC. 
The spring-loaded test 



probe has a heavy-duty, 
stainless-steel needle 
point set within a clamp- 
type jaw, allowing the clip to 
pierce the insulation of a 
cable up to 0.14-inch 
E3.5rnm) in diameter with- 
out damaging the insula- 
tion. The insulated tip 
assures that the desired 
wire or cable is safely and 
firmly grasped, and it 
avoids contact and shorts 
or grounding to adjacent 
machinery. A socket for a 
sheathed test lead connec- 
tion is located in the plung- 
er handle. 

Model 5784 clips are 
priced at $12.30 each— ITT 
Pomona Electronics, 1500 
East Ninth Street, P.O. Box 
2767, Pomona, CA 91 769: 
Phone: 714-469-2900: 
Fax: 714-629-3317. 

SMT PROTOTYPING 
BOARD. The SMT-1000 
p rot o board from Precision 
Circuit Technologies allows 
for the placement of more 
than one IC on the board. 
Measuring 2.9 x 4.75 
inches, it permits the pro- 
totyping of circuits with 
many IC's. 





CIRCLE 20 ON FREE 
INFORMATION CARD 



CIRCLE 21 ON FREE 
INFORMATION CARD 

Each SMT pad is con- 
nected to a plated-through 
hole that interconnects it to 
other points on the board 
with wire links. Two power 
busses simplify power con- 
nections. Most of the 
board's part footprints will 
accommodate more than 
one part size. The 
SOIC-16's will accommo- 
date 8-, 14-, or 16-pin 
SOICs; the SOIC-20W will 



accommodate a 16-or 20- 
pin wide-body SOIC or an 
8-.14-,or16-pinSOIC;and 
the SOIC-24W will accom- 
modate a 16-, 20-, or 24- 
pin wide-body SOIC or an 
8-, 14-, or 16-pin SOIC. 

Two PLCC areas permit 
great selection of PLCC 
sizes (20- to 100-pin 
PLCC's). A small section 
with through-hole pads 
spaced at 0.1 -inch is avail- 
able for combinsed AMD 
and leaded assembly. 

SMT- 1 000 protoboards 
are priced at $18.95 
each. — Precision Circuit 
Technologies. 10378 Fair- 
view Ave., Suite 152, 
Boise, ID 83704; Phone: 
208-327-0300, Ext. 2200. 

SELF-PULSATING USER DI- 
ODE. The RLD Series of 
self-pulsating, single-long- 
itudinal-mode, AIGaAs 
laser diodes from Rohm 
Electronics can, according 
to the manufacturer, re- 
duce the cost of fiber-optic 
transmission in LAN's and 
WAN's. The double-het- 
erostructure laser diodes 
can be modulated at fre- 
quencies of 1.2 GHz. 

The high modulation fre- 
quencies are achieved 
through the low junction ca- 
pacitance of the die's ac- 
tive area. They are man- 
ufactured by the molecular 
beam epitaxy (MBE) pro- 
cess which permits atomic- 
layer control in the growth 
of the structure. This, ac- 
cording to ROHM givers 
better control than is ob- 
taine with either liquid- 
phase epitaxy CLPE) or 
metalorganic chemical 
vapor deposition 
CMOCVD). 

RLD Series laser diodes 
typically operate at a 
threshold current of only 32 
milliamperes, significantly 
lowering power consump- 
tion, increasing switching 
speed, and giving longer 
operating life. Recent ac- 
celerated life tests of the 




CIRCLE 22 ON FREE 
INFORMATION CARD 

laser diodes by ROHM 
one sample lot at 50° 
with a constant 3 milliv\ 
optical output showec 
mean time to failure 
240.000 hours. This figi 
compares with the 20.0 
hours typical for laser 
odes in compact and vid 
disk players, 

RLD laser diodes < 
priced below $30 each 
volume. — Rohm Corpoi 
tion, address, Antioch, 1 

COMMUNICATIONS R 
CEIVER. According to 
manufacturer, the Lo\ 
HF-150 communicatio 
receiver puts the entire 
dio spectrum from 30 k 
to 30 MHz at your fing 
tips. That gives the lister 
access to internatior 
shortwave bands, amate 
ship and aircraft banc 
and time signals.The tuni 
rate is variable according 
the rotation speed of t 
main tuning knob. 

This rugged portable 
ceiver is made with sc 
hard alloy casings, me 
panels and machini 
parts. It measures or 
7.3x3.2x6.3 inches a 
weighs only 2.9 pounds 
can be operated from 
AC to DC adaptor Csl 
plied), an external 10 
15 — volt DC source, 
eight internal nickel- ce 
mium rechargeable / 
cells for 150 milliampe 
drain. 

Reception modes e 
AM, upper sidebai 
(USB), and lower sideba 
(LSB). which also allo\ 
reception of CW/RTT 
Fax, A phase-locked A 



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CIRCLE 23 ON FREE 
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system allows reception of 
selection of either syn- 
chronous lower sideband 
or synchronous upper side- 
band, and synchronous 
double sideband. That ar- 
rangement obtains the 
best reception from weak 
shortwave signals. 

In the dual-conversion 
design, the IF bandwidths 
of 2.5 kHz and 7 kHz are 
selectable, and the master 
oscillators are quartz crys- 
tals. Tuning frequency is 
displayed on a 5-digit LCD 
that also shows modes, 



memory information, and 
other important operating 
functions. Sixty memory 
channels, each storing fre- 
quency and mode, are pro- 
vided. 

The loudspeaker is inter- 
nal. Provision is made for 
external connections to 
headphones, external loud- 
speaker, and output for a 
tape recording. The re- 
ceiver can accept three dif- 
ferent antennas: 600-ohm 
long wire, 50-ohm coaxial 
feed, or a high-impedance 
whip. The rear panel has a 
socket for an optional key- 
pad, which allows direct 
frequency entry and instant 
direct memory access. 

The HF-150 receiver is 
priced under $600. — Elec- 
tronic Equipment Bank, 323 
Mill Street N.E., Vienna, 
VA 22180; Phone: 
703-368-3270; Fax: 
703-938-6911. 



AUTORANGING DIGITAL 
MULTIMETERS. The 

Tektronix DM2510 and 
DM2510G digital multi- 
meters, designed for 
benchtop use, offer full 
programmability with A y h- 
digit accuracy, an integral 
power supply, and auto- 
ranging or manual opera- 
tion. Functions provided by 
both units include voltage, 
current, or resistance mea- 
surement, true RMS AC 
voltage measurement 
(200-millivolts to 500-volt 
range). dB calculation, and 




CIRCLE 24 ON FREE 
INFORMATION CARD 



temperature measur 
ments. 

The meters measure C 
volts from 200 millivolts 
1000 volts with 0.03 
basic DC voltage accura< 
and DC amperes from 1( 
microamperes to 10 ar 
penes with 0.06% basic C 
amperes accuracy. Bo 
units are programmabl 
and the DM25 WG offe 
full programmability with i 
IEEE-488.1 interface. 

Front-panel keys simpli 
the selection of functic 
and range, and permit tl 
setting of GPIB addre; 
and termination parar 
eters. The TM2500 Seri< 
DMM's can be stacked t 
gether with other produc 
in the Tektronix TM250 ■ 
TM2500 Series to sa\ 
bench space. Besides d 
sign, manufacturing, ar 
service applications, Tr 
DMM's are said to ha\ 



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have broad applications in 
design manufacturing and 
service as well as training. 
The DM2510 is priced at 
$595 and DM2510G is 
priced at $695.— Tektronix, 
Test & Measurement 
Group. P.O. Box 1520, Pit- 
tsfield, MA 01202; Phone: 
1-800-426-2200. 

AUTOMATIC RCL METER. 

Fluke's PM 6303A auto- 
matic RCL meter is said to 
determine the value, di- 
mension, and equivalent 
circuit of passive compo- 
nents accurately over a 
wide range. The compo- 
nent is connected to the 
four-wire test fixture on the 
front panel of the instru- 
ment and the backlit LCD 
display shows the domi- 
nant component values 
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CIRCLE 25 ON FREE 
INFORMATION CARD 

trical dimension and one of 
the seven equivalent circuit 
diagrams. 

In addition its auto mode, 
the RCL meter permits 
users to select from nine 
different variables: series 
and parallel resistance, im- 
pedance, capacitance and 
inductance, phase-angle, 
plus dissipation, C with a 2- 
volt DC bias, and Q-factor. 
Each function can be di- 
rectly accessed with a 
front-panel button. A press 
of the trim button elimi- 
nates any errors intro- 



duced by either a test cable 
or a test fixture. 

The PM 6303A automat- 
ic RCL meter, equipped 
with a four-wire test fixture, 
an operating manual, and a 
line cord, is priced at 
$1500— John Fluke Mfg. 
Co., Inc.. P.O. Box 9090, 
M/S 250E, Everett, WA 
98206-9090: Phone: 
800-44-FLUKE. 

RF DETECTOR OS- 
CILLOSCOPE PROBE KIT. 

This kit is for an RF-detec- 
tor oscilloscope probe with 
a bandwidth of 800-MHz. 
Intended for use with any 
oscilloscope having a 10- 
megohm input. Pomona 
Eiecttvnics' Model 5815 kit 
contains interchangeable 
oscilloscope probes and 
accessories for the profes- 
sional oscilloscope user. 
The RF detector os- 
cilloscope probe kit is 




CIRCLE 26 ON FREE 
INFORMATION CARD 

packaged in a reusable 
plastic case, and replace- 
ment parts are readily avail- 
able. The probes' modular 
design permits maximum 
flexibility and inter- 
changeability of tips and 
various types of interface 
connections. 

The Model 5815 RF-de- 
tector oscilloscope probe 
kit is priced at $70.50. — 
ITT Pomona Electronics, 
1500 East Ninth Street, 
P.O. Box 2767, Pomona, 
CA 91769; Phone: 
714-469-2900; Fax: 
714-629-3317. Ft-E 



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A practical toolbox reference for 
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Emphasizing the importance of 
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32 



ENCYCLOPEDIA OF ELEC- 
TRONIC CIRCUITS: Volume 
4; by Rutioli F. Graf and 
William Sheets. TAB Books, 
Division of McGraw-Hill 
Inc., Blue Ridge Summit, PA 
17294-0850; Tel. 
1-800-822-8138; $29.95. 

Hundreds of schematics 
for up-to-date electronic 
circuits, straight from the 
drawing boards of industry 
leaders such as Motorola. 
Texas Instruments, Gener- 
al Electric, and National 
Semiconductor, are in- 
cluded in the 700-plus 




CIRCLE 27 ON FREE 
INFORMATION CARD 

pages of this book. Tightly 
organized and extensively 
indexed, the book includes 
complete descriptions of 
automotive, audio, video, 
ultrasonic, alarm and secur- 
ity, and computer-related 
circuits. The book's index 
includes not only the cir- 
cuits presented in Volume 
4, but also those that ap- 
pear in the first three vol- 
umes. The circuits are 
arranged in 104 chapters, 
with circuit titles listed at 
the beginning of each chap- 
ter for easy reference. AS- 
most every circuit is ac- 
companied by a brief 
written explanation; those 
who require more details 
can order the original 
sources, which are listed in 
the back of the book. 



BUILD YOUR OWN SPEC- 
TRUM ANALYZER; by Murray 
(WA2PZ0) and Bruce 
(WA2DR0) Barlowe. Sci- 
ence Workshop, Box 310, 
Bethpage, NY 11714; Phone: 
516-731-7628; S24.95. 

A spectrum analyzer is a 
valuable — and expen- 
sive — piece of test equip- 
ment with dozens of 
applications. But profes- 
sional models, costing 
thousands of dollars, are 
beyond the means of most 
electronics hobbyists and 
many professionals. This 
book shows how to build 
the "Poor Man's Spectrum 
Analyzer" for a fraction of 
the cost. The instrument 
does "almost everything 
the professional models 
do," but requires "a little 
more effort and ingenuity" 
on the part of the user 
when it comes to making 
precise measurements. 
The analyzer can use al- 
most any standard os- 
cilloscope for its display. 
The Poor Man's Spectrum 
Analyzer is packaged as a 
kit, available separately. 

The book includes a tu- 
torial covering theory of op- 
eration, layout drawings 
and photographs, and 
magazine articles about 
the spectrum analyzer, re- 
printed from Ham Radio 




and Communications Re- 
view, In addition, it features 
a chapter titled "User 
Feedback" in which actual 
user modifications are pre- 
sented and explained in de- 
tail. The final chapter 
includes copies of the in- 
structions, schematics, 
and parts layouts for each 
of the modules used in the 
spectrum analyzer. 

MOBILE-ANTENNA WALL 
CHART; from The Antenna 
Specialists Co., 30500 
Bruce Industrial Parkway, 
Cleveland, OH 44139-3996; 
Phone: 216-349-8400; Fax: 
216-349-8407; free to deal- 
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This full-color wall chart 
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tenna for every vehicular in- 
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54 x 38-inch chart pre- 
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150 professional mobile- 
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The antennas are cross-ref- 
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inch hole mounts, trunk lid, 
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lutions for special applk 
tions including those 
motorcycles and railroat 
Each antenna is depictec 
a photograph with its co 
ponents identified by p; 
number. 

HIGH PERFORMANCE PC/, 
DATA ACQUISITION PRO! 
UCTS; from Analogic Corp 
ration, 360 Audubon Roa 
Wakefield, MA 0188 
Phone: 508-977-3000; Fa 
617-245-1274; free. 

This 64-page catalc 
features data acquisitk 
products with a broe 
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those with 12- to 16-bit a 
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quisition boards conta 
analog output capabilitie 
counter-timers, and digil 
input/output. The catalc 
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boards, and signal-co 




CIRCLE 30 ON FREE 
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ditioning boards, as well ; 
PC-based frame grabber 
In addition to hardwa 
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fers high level languac 
CHLL) drivers, set-up ar 
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« TO ORDER 
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1-800-292-7711 
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Hitachi RSO Series 

(Portable Real-time Digital Storage Oscilloscopes) 



VC-6023 


20MHz, 20MS/S 


$1,695 


VC-6024 


50MHz. 20MS/S 


$1 ,995 


VC-6025 


50MHz, 20MS/S 


$2,195 


VC-6045 


100MHz, 40MS/S 


Call 


VC-6145 


100MHz, 10QMS/S 


Call 



SPECIAL BUY 

V-212- 20MHz Scope $409 



BSO's Irom Hitachi lealurg roll mode, averaging, save 
memory, smoothing, interpolation, pro-triggering, cursor 
measurements. These scopes enable more accurals, 

simpNer observation of compJex waveforms, in addition to 
such functions as nardcopy via a plotter interface and 
waveform transfer via the HS-232C interface. Enjoy the 
comfort ol analog and the power to digital, 

25MHz Eienco Oscilloscope 



Hitachi Portable Scopes 

DC lo 50MHz, 2-Channet, DC offset (unc- 
tion, Alternate magnifier function 

V-525 - CRT Readout, Cursor Meas, $935 

V-523 - Delayed Sweep . $975 

V-522 - Basic Model . $875 

V-422 - 40MHz . $775 

$695 
S625 



■ 40MHz 

V-223 - 20MHz delayed sweep. 
V-222 ■ 20MHz deluxe " 



$349 




S-1325 
« Dual Trace 
1mV Sensitivity 
• 6' CRT 
• XY Operation 
• TV Sync 
* (2) 1x, 10x Probes included 



PRICE BREAKTHRU 



20MHz Digital Storage Oscilloscope 

• Analog/Digital Scope 

• 2K word per channel memory DS203 

• lOMS/s sampling rate . 

■ Sta^ot-art technology $775 

■ Includes probes 

S-1360 60MHz Delay Sweep $775 



HITACHI COMPACT SERIES SCOPES 

This series provides many new fu rations such as CRT 
Readout. Cursor measurements [V- 1 0BE.-'1 0E5A. ; 6S6A), Fre- 
quency Ctr (V-10B5), Sweeplime Auto ranging. Delayed 
sweep and Tripper Lock using a 6-inch CRT.You dent teel 
the compactness it, lenns c: pertG-irnance end operation 

V-660 - 60MHz, Dual Trace $1,149 

V-665A - 60MHz, DT, w/cursor $1 ,345 

V-1060 - 100MHz, Dual Trace $1,395 

V-1065A- 100MHz. DT, w/cursor $1,649 

V-1085 - 100MHz, QT, w/cursor $1,995 

V-1100A- 100MHz. Quad Trace $2,195 

V-1 150 - 1 50MHz, Quad Trace , $2,695 

Elenco 40MHz Dual Trace 

^— _ *%& K!i 

S-1340 
■ • High luminance 6" CRT 

• 1 mV Sensitivity 
I; >10KV Acceleration Voltage 

• 9ns Rise Time 
• X-Y Operation 

■ Includes (2) 1x, 10x Probes 




All scopes include probes, schematics, operators manual and 3 year (2 yrs for Elenco scopes) world wide warranty on parts & labor. Many accessories available (or all Hitachi 
scopes. Call or write tor complete specifications on Ihese and many other line oscilloscopes, Ix, 1 Ox Scope Probes: P-l 65MHz $17.95, P-2 100MHz $21.95 



Digital Capacitance Meter 

CM- 15508 

$58.95 

9 Ranges 

.1 pi 20.000uld 

.5% basic accy 

Zero control w/ Case 

Big r Display 




| Digital LCR Meter 
LC-1801 

$125 

Measures: 

Colls luH-ZOOH 

Caps.1pl-2tMu1 

Hes .01-2DM 




finn_ 




Muiti meter with 
Capacitance * 
Transistor Tester 

$55 CM-1500B 

Reads Volls. Ohms 

Cunent, Capacitors. 

Transistors and 

Diodes / with case 



FLUKE MULTIMETERS 



Scopemeters 
Model 93 

Modal 95 
Modal 97 
10 Series 
Model 10 

Model 12 



(All Models Available Call) 



$1 .095.00 
$1,395.00 
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$62.95 
$79.95 



70 Series 
Model 70II 
Model 77II 
Model 79II 
60 Series 
Model B7 



$65.00 
$145.00 
$169.00 

$289.00 



Quad Power Supply XP-580 

l$ 69.95 




2-20V @ 2A 

12V@1A 

5V@3A 

-5V @ .5A 



Fully regulated and short circuit protected 



Triple Power Supply XP-620 
Assembled 475 
Kit $50 

2lo1$V@1A, 
-2lo-15V@1A 
(or4lo30V@1A) 
aad5V@3A 
All the desired Features lor doing experiments. 
Features short circuit protection, all supplies 




AM/FM Transistor 

Radio Kit 
with Training Course 

Model AM/FM 1 0S 

$26.95 

14 Transistors * 5 Diodes 
Makes a great school project 




True RMS 4 1/2 

Digit Multimeter 

M-700T 

$135 

.05% DC Accuracy 

.1% Resistance 
with Freq. Counter 
Data Hold 



GF-8Q1 6 Function Generator 

with Freq. Counter 

$249 

Sine, Square, Triangle 
Pulse. Ramp, .2 to 2MHi 
Freq Counter ,1 - 10MHz 
I nt/Exl operation 
GF-8015 without Freq. Meter $179 



I .jjiriiVHl' 



Function Generator 
Blox 
#9 600 
$28.95 

Provides sine, triangle, square 

wave Irom IKzId IMHj 

AM or FM capability 




Learn to Build and Program 
Computers with this Kit 

Includes: AU Parts. Assembly and Lessen Manual 

Model 
MM-8000 



Wide Band Signal 

Generators 




$129.00 




Stamina irwn scratch you burJd a compter *y*tom. Ojr 
Micro-Master trainer teachers you to write rnkt RAMs. 
ROMs and run * BOSS micro processor, which uses 
:.i n ■ i 1. 3 ■ machine- language as 1 SM PC , 



SG-9000 $129 
RF Frog 1Q0K-45OMH2 AM Modula- 
tion ol IKHz Variable RF output 
SG-9500 til Digital Display & 
150 MHz built-in Counter S249 



LASER KITS 

Build your own laser. This great hit Includes all parts needed lo build a class II laser. 

Safe to use. oulpul is under one milltwalt. Kit Includes a new Ne-Ne 1.1 25 die x 5.75' 
long laser lube. Comes with building instructions, schematic and all pans. 

Model LK-1 $79,95 



Specifications LK-1 : 

Input voltage 1 2 VDC @ 1 .25 amp 

Output voltage 2-3KV @ 3-4.5MA 

Trigger voltage 6-8KV 

Laser power 1 milliwatt 

Laser tube type helium - neon 

Laser tube size 1.125" dia x 5.75" long 



Mirror & Motor Kit 

This unique kit allows you lo projeel laser patterns on Ihe ceiling or walls. You change 
the patterns by varying the speed of Ihe motors. The kit comes complete will) Z 
motors, 2 front surface minors, 2 motor brackets and 1 power rheostat control to vary 
speed ol the motor. 

Model LM-1 $19.95 




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AIWA CSD-EX1 

PORTABLE LCD 

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• High power output 

• Power saving switch plus auto stop 
- 20seleetfon random programmable 

memory CO 

• AM wlde/FM stereo tuner 

(awmjti our price 

sum Retail 179.95 $-11095 



T NEW! i 




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AIWA NSX-330 

30W/CH HI-FI MINI COMPONENT 
SYSTEM WITH SURROUND SOUND 

• Super T-oass 
Includes 

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random preset 

- du ai auto reverse cass wr oolEy B NR 

- optical digital output terminal 

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Sugg. Retail '560.00 SVQQ95 




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(CAN-SWa 



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AM/FM STEREO CASSETTE 
PLAYER WITH AUTO REVERSE 

• Ultra compact sire 

• Digital synthesiser tuner 
with 7AM /7FM presets 

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• one button wired remote 
includes: 

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IPAN-27K: 0ur prtce 

Sugg. Retail '209.95 $<4eQ95 





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Broadcasts up to 9 ft. 

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our prtce 




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■ LEO readout 

* ti-function tone remote 

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iPAN-93001 our Price 

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34 



BUILD THIS 



HANDI-TALKIE 



DON WRAY 

IF VOU EVER WANTED TO BUILD A 

small powerful handheld trans- 
ceiver and, at the same time 
leam surface-mount technology 
(SMT). this is the project for 
you! The E-Comm frequency- 
modulated (FM) transceiver is 
housed in a rugged yet attrac- 
tive aluminum case less than 
six inches long. U is one of the 
most unusual transmitter-re- 
ceivers ever designed for its 
power level and operating fre- 
quency range. The case in- 
cludes a rechargeable nickel- 
cadmium power pack that will 
save you the cost of periodically 
replacing eight AA alkaline 
cells. 

The E-Comm receiver has a 
respectable 0.3-microvolt sen- 
sitivity (12-dB SINAD) for high 
quality reception, and Us trans- 
mitter boasts at least a 90% effi- 
ciency. E-Comm owes its effi- 
ciency to its innovative Class-E 
final amplifier which exhibits 
high power gain. It offers a con- 
tinuous output of 3 watts rms 
into a 50-ohm antenna or 
dummy load. The efficient re- 
ceiver and the rechargeable 
power supply make it possible 
to keep E-Comm on the air in 
the squelch mode for 80 hours 
without recharging the power 
pack. 

Intended for narrow-band 
FM. E-Comm has a usable car- 
rier frequency range of 27 MHz 
to 32 MHz with only crystal and 
alignment changes. The subject 
of this article is a version de- 
signed for 27.145-MHz opera- 
tion. With modifications to the 
transmit and receive fillers 
(component value changes) op- 
eration up to 60 MHz is possi- 
ble. This allows the transceiver 
to work both the six- and ten- 
meter amateur radio bands. 
Note: This transceiver has not 



Build this efficient, miniature FM 

handheld transceiver and start your own 

private communications network. 




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FIG. 1— SCHEMATIC SHOWING THE MODULATOR TRIPLE R. Class-E amplifier, li miter, 
driver and low-voltage regulator sections of the E-Comm transceiver. The key device is 
IC1, the FM transmitter chip. 



been submitted for FCC ap- 
proval, and its operation on cer- 
tain frequencies may not be 
allowed and/or may require li- 
censing. 

The top panel controls of E- 
Comm include an on-off 
switch, volume and squelch 
knobs and an LED power-pack 
status indicator. The removable 
flexible seven-inch antenna is 
coupled to the transceiver with 
a 50-ohm bayonet-style BNC 
connector plug. All die compo- 
nents except the battery pack, 
microphone, and speaker are 
mounted on the double-sided 
PC board. Extensive use of inte- 
grated circuits and surface- 
mounted components allows 
the circuitry to fit on a PC board 
that measures only 2.25 x 3.1 
inches. 

How it was designed 

The transceiver has three 
main sections: transmitter, re- 



ceiver, and power supply. (Refer 
to Figs. 1 and 2.) The transmit- 
ter is designed around Motor- 
ola's MC2833, a low-power FM 
transmitter IC whose plnout 
and functional block diagram 
are given in Fig. 3. The receiver 
is designed around Motorola's 
MC3363, a low-power, dual-con- 
version FM receiver IC whose pi- 
nout and block diagram are 
given in Fig. 4. 

Received signals picked up by 
the antenna are preselected by 
the five -pole transmit bandpass 
filter consisting of inductors L4, 
L7, and L5 and capacitors Cll, 
C2, and C30 as shown on the 
right side of Fig. 1. The received 
signal is then fed through the 
receive/transmit switch Sl-b to 
an impedance-matching stage 
consisting of CIO and L3 shown 
on the left side of Fig. 2. That 
stage provides an additional 
two poles of preselection. 

Diodes Dl and D2 prevent 



overloading and the possible c 
struction of the RF amplif. 
transistor if it is subjected 
overdriving at the front er 
The preselected signal is th 
amplified by the IC3 (MC33C 
internal common-emitter 1 
amplifier stage and fed to t 
first mixer stage on pin 1 . 

The RF amplifier provides 
gain of approximately 20 d 
The first local oscillator (L 
takes a third overtone from 
crystal, and drives the first m 
er through an internal casco 
amplifier. Downconversii 
makes the first LO frequen 
(the first IF frequency) 10. 7 M 
greater than the carrier. For < 
ample, if a 27,145 MHz carr 
were present, the crystal f: 
quency would be 27.145 M: 
plus 10.7 MHz or 37.845 Mt 

The mixer is a doubly b 
anced multiplier that provic 
about 18 dB of conversion ga; 
The output of the mixer is 
emitter-follower stage with 
output impedance of 330 ohi 
to match the ceramic filter, f 




FiG.2— SCHEMATIC SHOWING FM RECEIVER, audio filter, and audio amplifier sec- 
tions of the E-Comm transceiver. The key device here is IC3, the dual-conversion FM 
receiver chip. 



ter F2, a 10.7-MHz ceramic 
bandpass filter, removes un- 
wanted out-of-band harmonics 
from the output of the first mix- 
er. The second mixer takes a sig- 
nal from the 10.245-MHz funda- 
mental mode crystal-controlled 
oscillator XTAL2 whose output 
is mixed with the 10.7-MHz first 
IF to generate the 455-kHz sec- 
ond IF with a conversion gain of 
approximately 21 dB. 

The 455-KHz ceramic filter Fl 
(left side of IC3 in Fig. 2) pro- 
vides narrow-band filtering for 
the limiter amplifiers within 



IC1, the MC2833 FM transmit- 
ter chip. The limiters clip the 
455-kHz second IF signal to re- 
move unwanted amplitude- 
modulated signals and feed the 
audio detector. A quadrature de- 
tector within IC3, the MC3363, 
detects the modulated signal. 
The parallel quadrature detec- 
tor tank, LIO, in the detector is 
tuned to 455 KHz. 

The demodulated (audio) sig- 
nal on pin 16 of the FM trans- 
mitter IC1 is then filtered by an 
active filter stage that includes 
an op-amp within IC3, the FM 



receiver chip in Fig. 2. This ac- 
tive filter, connected at pins 15 
and 19 of 1C3 and consisting of 
capacitors C13, C24, and C15 
and resistors R21, R22, R23, 
and R15, has a roll off at 3 kHz 
Squelch is performed by the 
carrier-detect function on pin 
13 of the FM transmitter chip, 
IC1 in Fig. 1. Resistor RIO (be- 
tween pins 12 and 13) provides 
hysteresis in the squelch circuit 
to prevent unwanted "break 
through." This squelch circuit 
is unusual; its output both en- 
ables and disables IC4, a 
Motorola MC34119D low-power 
audio amplifier with a chip dis- 
able pin 1 (CD). 










VARIABLE 
REACTANCE 



RE 
OSC 



-WV— *-v*v 



-f— f 1 MIC 

B2±. 



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PARTS LIST 



13 



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38 



FIG. 3— PINOUT AND FUNCTIONAL 
block diagram for IC1, the Motorola 
MC2833 low-power FM transmitter chip. 

Power consumption is re- 
duced by disabling the audio 
amplifier when the receiver is 
squelched, and it is also kept 
low because it is run from the 
unregulated power supply in 
combination with the 32-ohm 
speaker. This arrangement 
holds receiver consumption 
down to only 7 milliamperes 
from the battery pack when the 
receiver is in the squelch mode. 
The gain of the audio amplifier 
is set by resistor R29 (between 
pins 4 and 5) and nearby re- 
sistor R24, and is expressed as 
(2 X R29/R24). 

The transmitter is a 3-watt 
narrow-band FM Class E circuit 
with efficiency greater than 
90% . The front end of the trans- 
mitter is based on 1C1 (Fig. 1), 
the low-power FM transmitter 
chip. The voice signal is picked 
up by the microphone and fed to 
the mic amp input on pin 5 of IC1 . 
Resistor Rll (between pins 4 
and 51 sets the gain of the am- 
plifier, and the output of the am- 
plifier drives the FM modulator. 

A variable reactance in the 
modulator "bends" the frequen- 
cy of the crystal-controlled os- 
cillator. Because the crystal 
frequency cannot be deviated by 
more than a few kilohertz by the 
variable reactance circuit, a 
multiplication scheme derives 
the proper carrier and modula- 
tion frequencies. In the E- 






Resistors (All 1206 SUD chip re- 
sistors are 1/8-watt, 5%, unless 
otherwise specified) 

R1 — 47 ohms, 1/2-watt, 5%, radial- 
lead 
R2— 22 ohms, 1206, SMD 
R3— 47 ohms, 1206, SMD 
R4— 220 ohms, 1206, SMD 
R5— 330 ohms, 1206, SMD 
R6— 470 ohms, 1206, SMD 
R7— 1000 ohms, 1206, SMD 
R8, R9— 4700 ohms, 1206, SMD 
R10— 4.7 megohms, 1206, SMD 
R11. R12— 22,000 ohms, 1206 

SMD 
R13, R24— 10,000 ohms, 1206 

SMD 
R14, R15— 47,000 ohms, 1206 

SMD 
R16-R23— 100,000 ohms, 1206 

SMD 
R25, R26— 100,00 ohms potenti- 
ometer. Bourns 51CADD12A20, 
or equivalent 
R27— 330,000 ohms, 1206 SMD 
R28— 390,000 ohms, 1206 SMD 
R29— 680,000 ohms, 1206 SMT 
R30— 510,000 ohms, 1206 SMT 
R31 — current variable resistor, poly- 
mer-based, Raychem Polyswitch 
RXE040 or equivalent 
Capacitors 

C1— 5 pF NPO 805 SMD ceramic, 
Tayio-Yuden UMK212CH0R5D- 
B or equivalent 
C2— 22 pF NPO ceramic disc, 100- 
volt, Panasonic ECC- 
F2A220JCE or equivalent 
C3, C4— 47 pF NPO 805 SMD ce- 
ramic, Tayio-Yuden UMK- 
212CG470K-B or equivalent 
C5— 56 pF NPO 805 SMD ceramic, 
Tayio-Yuden UMK212CG560K-B 
or equivalent 
C6-C10— 68 pF NPO 805 SMD ce- 
ramic, Tayio-Yuden UMK- 
212CG680K-B or equivalent 
C11— 82 pF NPO ceramic disc, 100- 
volt, Panasonic ECC- 
F2A820JCE or equivalent 
C12— 120 pF NPO 805 SMD ce- 
ramic, Tayio-Yuden UMK- 
212CG121K-B or equivalent 
C13— 330 pF NPO 805 SMD ce- 
ramic, Tayio-Yuden UMK- 
212CG331K-B or equivalent 



Comm, a crystal frequency 
equal to one-third of the carrier 
frequency was chosen. Inductor 
L9 (in series with XTAL3 be- 
tween pins 1 and 16 of IC1) cen- 
ters the oscillator frequency 



C14, C15— 470 pF NPO 805 Slv 

ceramic. Tayio-Yuden UM 

212CG471K-B or equivalent 
C16, C26. C27— 0.01 |iF Y5V 8( 

SMD ceramic, Tayio-Yudt 

UMK212F103Z-B or equivalent 
C17-C23— 1000 pF NPO 805 SW 

ceramic, Tayio-Yude 

UMK212SL102K-B or equivale 
C24— 1500 pF X7R 805 SMD C 

ramie, Tayio-Yuden UMI 

212B152K-B or equivalent 
C25, C29, C31-C36— 0.1^F YE 

805 SMD ceramic, Tayio-Yud* 

UML212F104Z-B or equivalent 
C2& — designation not used 
C30— 8-50 pF trimmer capacrk 

Sprague-GM GKG50011 i 

equivalent 
C37-C40, C42, C43, C46— 1p 

1206 SMD tantalum, 16-volt 
C41 — designation not used 
C44— 10|xF electrolytic, 16-volt, J 

mm, Panasonic ECE-A1CGE1C 

or equivalent 
C45— 100|iF electrolytic, 16-voi 

6.3 mm, Panasonic ECE 

A1CGE101 or equivalent 
Semiconductors 
D1, D2— DL4148 switching diod. 

1206 SMD, 
D3— DL4003 silicon rectifier, SM 
D4— 1N475BA 56-volt Zener dioc 
LED1— HLMP-1 503-101 (Hewlet 

Packard) green light-emitting c 

ode right-angle indicator c 

equivalent 
Q1, Q2— MPF6660 power FE" 

(Motorola) or equivalent 
1C1— MC2833 (Motorola) low 

power FM transmitter systei 

SMD 
IC2— 74 AC L1 11 32 (Texas Instn 

ments) quad NAND gate, Schmi 

trigger, SMD or equivalent 
IC3— MC3363DW (Motorola) lov 

power dual-conversion FM re 

ceiver, SMD package 
IC4— MC34119 (Motorola) low 

power audio amplifier, SMD 
IC5— MAX666CSA (Maxim) vol 

age regulator, SMD package 
Inductors 
L1-L3— 0.33 p.H, adjustable coi 

Toko, 292KNAS-T1034Z C 

equivalent 



when no modulation is applie 
The buffered output of the o 
dilator on rf output pin 14 th« 
feeds a tank circuit made up 
inductor LI and capacitor C 
which is tuned to the third he 



PARTS LIST 



L4, L5— 0.68 p,H, axial-leaded in- 
duclor, Taiyo-Yuden, 

LAL04NAR68M or equivalent 

L6— 1.2 n-H SMD inductor, 2.5 x 
3.2mm or equivalent 

L7 — 1.8 nH axial-leaded inductor, 
Taiyo-Yuden LAL04NA1R8M or 
equivalent 

L8 — 2.7 p,H axial-teaded inductor, 
Taiyo-Yuden LAL04NA2R7M or 
equivalent 

L9— 10 jjlH adjustable inductor, 
Toko F292CNS-T1052Z or equiv- 
alent 

L10— quad coil, Toko 5SVLC- 
G6378JT or equivalent 

Switches 

S1— DPDT pushbutton switch, 
(Schadow) F2UOA or equivalent 

S2— SPDT slide switch, C&K, 
1101M2S3AQE2 or equivalent 

Connectors 

J1 — 50-ohm BNC bayonet-style, 
PC- board- mount jack with two 
hex ring nuts 

J2— charging jack, Cui Stack 
PJ-002A or equivalent 

J3 to J5 — sockets, 2-pin 2mm, Mo- 
lex 53014-0210 with three 2-pin 
plugs, 2mm, Molex 51004-0200 
and six pins, Molex 5001 1 -81 00 or 
equivalent 

Crystals 

XTAL1— 37.845-MHz third-over- 
tone crystal, Toyocom, HC-49 or 
equivalent 

XTAL2— 10.245-MHz parallel- 
mode crystal, 32 pF, Toyocom, 
HC-49 or equivalent 

XTAL3— 9.0483-MHz parallel- 
mode crystal, 32 pF, Toyocom, 
HC-49 or equivalent 

Filters 

Fl — 455-kHz ceramic filter, Murata 
CFUM455E or equivalent 

F2 — 10.7-MHz ceramic filter, Toko 
SK107M5-A0-10 or equivalent 

Other Components 

MIC1— microphone, Panasonic 
WM-54BT or equivalent 

SPKR1 — speaker, 2-inch square, 
32-ohm, Regal, SA-200 or equiv- 
alent 

ANT1— flexible coil antenna with 
BNC bayonet-style plug. 




monic of the oscillator. 

The signal is multiplied by a 
factor of three to obtain the car- 
rier frequency in this tank cir- 
cuit. Both the carrier and the 
modulation signal are multi- 



Miscellaneous: PC board, 
custom-made battery pack with 
eight rechargeable nickel-cad- 
mium AA cells, No. 24 AWG wire; 
one 120- volt AC to 12- volt DC 
adapter for charging the power 
pack; custom-made extruded 
case with bottom panel and silk- 
screened top panel; one custom 
made speaker grill; two knobs, 
Keystone, 8580 or equivalent 
with two hex ring nuts each; four 
No. 440 x 3/8-inch Philips-head 
screws, black; four No. 6-32 X 
5/16-inch Philips-head screws, 
black; four No. 6-32 internal -tooth 
lock washers, four No. 6-32 hex 
nuts, one perforated hole plug. 
Hayco 2637 or equivalent; six- 
inch length of shielded wire; 12- 
inch length of No. 24 AWG wire; 
fine solder wire; tools and ac- 
cessories as specified in the text. 

NOTE: The following parts are 
available from Micro Advance- 
ment Products, Inc., P.O. Box 
8505, Hollywood, FL 33084 
800-358-8545 

• Printed circuit board only — 
$12,00 

• Kh with printed circuit board 
and all components— $97.00 

• Enclosure including all hard- 
ware, microphone, speaker, 
knobs and transmit button— 
$38.00 

• Battery pack— $17.95 

• AC to DC adapter for charging 
power pack, wall outlet 
mount — $7.85 

• Flexible "rubber ducky" 
seven-inch 27-MHz antenna 
with BNC bayonet-style plug — 
$17.95 

• Complete kit for one E-Comm 
transceiver — $168.00 

• Complete kit for two E-Comm 
transceivers — $297.00 

• One E-Comm transceiver as- 
sembled and tested — $229.00 

Please add $4.95 for shipping 
and handling to all orders. Free 
frequency modification sheet 
and crystal list with each order. 



plied to obtain the 5-kHz devia- 
tion required by the receiver. 
Next the signal is passed 
through a tuned common-emit- 
ter amplifier to amplify and 
smooth the carrier. 



Next the signal is clipped by 
the quad nand Schmitt trigger, 
IC2, a 74AC11132 high-speed 
CMOS logic gate. Two sections 
of IC2 (IC2-b and IC2-c) provide 
drive to turn a parallel-con- 
nected pair of enhancement- 
mode MPF6660 power 
MOSFET's, 91 and Q2, on and 
off. Class E operation is ob- 
tained with the fast switching 
as well as the low on resistance 
of the power MOSFET's. 

Theoretically, if no power were 
required by the switch for ac- 
tivation (driver power), and if it 
were lossless, E-Comm would 
be nearly 100% efficient. Al- 
though the FET's do not form a 
perfect switch, they offer several 
useful characteristics: The in- 
put power required to drive the 
FET's is very low (drawn prin- 
cipally in switching the gate in- 
put capacitance on and off at 
high speed (less than 6 nanose- 
conds), and their switching 
speed is very high. 

Those characteristics give the 
transmitter an efficiency of 
about 90%, measured as the 
ratio of rms RF power (delivered 
to the 50-ohm load) to the DC 
supply. A five-pole filter matches 




FIG. 4— PINOUT AND FUNCTIONAL 
block diagram for IC3, the Motorola 

MC3363DW low-power, dual-conversion 
FM receiver chip. 



2? 



I 

s 

o 

2 



e 

■5 

LU 



40 




J 

R25 




., 





FIQ. 5— PARTS PLACEMENT DIAGRAM for the E-Comm transceiver, Note radial lead- 
ed components C2. C11, R30 and F2. Axial leaded components R1, L4, L5, L7, L8 and 
D4 are vertically mounted. 



the output of the MOSFET 
switches to the antenna imped- 
ance while also filtering. 

Variable capacitor C30 fine 
tunes the output stage to match 
the antenna or dummy load. 
Notice that to obtain class E op- 
eration, both the toad and the 
multiplier stages must be tuned 
in accordance with instruc- 
tions in the Calibration and 
Tuneup section of this article. 
Mismatch and overload protec- 
tion are provided by Zener 
clamp D4 {Fig.l, between Ql 
and Q2) as well as the Poly- 
switch protective resistor R31 
(Fig. 2, upper left) in the power 
supply. 

The low-voltage regulator 
shown in Fig. 1 includes a 
CMOS voltage regulator IC5, a 
Maxim MAX666, which con- 
serves power and provides two 
features: low quiescent current 
of about 15 microamperes and a 
built-in low-battery detect func- 
tion. The regulated output is set 
by resistor R18 (pin 6) and R28 



to be 6.4 volts. This voltage level 
was chosen to provide enough 
gate voltage to switch power 
MOSFET's Ql and Q2 on hard 
without exceeding the max- 
imum voltage specification of 
the quad nand gate IC2. 

The low-battery detect circuit 
is set by resistors R17 and R30 
at lbi pin 3 of IC5 to about 8 
volts. Because the voltage reg- 
ulator is a CMOS device, high 
resistor values are placed in the 
feedback loops for further re- 
duction of power consumption. 
Pin 7 of IC5 lbo has an open- 
drain output that drives the 
low-battery indicator LED1. 

The receive/transmit switch 
Sl-a turns the receive and 
transmit sections of the trans- 
ceiver on and off for further 
power conservation. The power 
pack consists of eight AA nickel- 
cadmium rechargeable cells, 
each with a rating of 1 . 2 volts at 
500 milliampere hours. The 
pack is charged through con- 
nector J2 (Fig. 1 , upper left) by a 



120-volt AC to 12-volt unrej 
lated DC adapter plugged ii 
the AC line. 

Building the transceiver 

Surface mount devices (SN 
were chosen for E-Comm 
cause they permit the ct 
struction of a miniature tra 
ceiver, and their small com; 
nent dimensions help to k< 
PC board traces short. The 
fore, by building this trai 
ceiver you'll get a leg up on \ 
whole process of surface-moi 
technology (SMT) because > 
will gain hands-on experiei 
in picking and placing the mi 
ature components and 
awareness of both the bene: 
and drawback to SMT. Howei 
do not attempt to construct t 
transceiver unless you are 
accomplished project buildei 

Transceiver assembly 

Many SMD components ; 
not marked with values or i 
ings because of the limil 



space on their cases. This 
means that you must be ex- 
tremely careful to avoid mixing 
up chip components before and 
during construction. 

Specialized tools should be 
used in picking and placing 
SMD components. They should 
be suitable for grasping small, 
hard-to-handle parts. Recom- 
mended are stainless steel nee- 
dle-point curved-end jeweler's 
tweezers for picking and plac- 
ing small parts such as chip re- 
sistors, capacitors and diodes 
on the circuit board, Fine jew- 
eler's pliers will be useful for 
straightening stub leads on sur- 
face-mount IC's. 

Do all soldering with a fine- 
tipped 10- to 15-watt pencil-type 
soldering iron. A lighted magni- 
fying glass will be helpful, pref- 
erably one that mounts on the 
edge of a bench. Use only high- 
quality fine (0.01- to 0.02-inch} 
diameter solder wire and a suit- 
able liquid flux. Keep fine sol- 
der-removing braid on hand to 
correct any mistakes that you 
might make. 

Anyone building E-Comm 
should be mentally prepared for 
the surprisingly small size of 
the SMD components and their 
close spacing. Working with 
SMD components calls for near 
professional quality soldering 
skills and a lot of patience. Set 
up for building E-Comm on a 
well lighted desk or bench and 
sit in a comfortable chair. Do 
not start this fine work unless 
you are rested and relaxed; mis- 
takes can be costly and frustrat- 
ing to correct! 

Refer to the parts placement 
diagram. Fig. 5. Be sure to ob- 
serve all conventions when 
mounting polarized compo- 
nents such as diodes and capac- 
itors. Dots on the PC board 
denote polarity. Position all po- 
larized capacitors so the 
positive lead is nearest the dot, 
and position all diodes and rec- 
tifiers so their cathodes are 
nearest the dot. Be sure to find 
the markers indicating pin 1 on 
all SMD packages. It is typically 
a white dot. 

Do not attempt to build this 
circuit on any PC board except 
one that has been specifically 
designed for this circuit. Failure 




FIG. 6— CUTAWAY VIEW OF ASSEMBLED E-Comm TRANSCEIVER showing the posi- 
tions of the controls and the locations of the microphone, speaker, loaded circuit 
board and power pack. 



to observe this will result in a 
poor performing transceiver. A 
proper PC board for RF circuitry 
needs an adequate ground 
plane and short interconnects 
to prevent Inadvertant oscilla- 
tions, loss of sensitivity, and 
noise-related problems. 

The accurate and effective 
mounting of SMD components 
requires a solder mask on the 
PCB because of the cramped 
lead spacing. A double-sided 
board with plated-through 



holes and solder mask is avail- 
able from the source given in 
the Parts List. It can be pur- 
chased as a single item or as 
part of the options listed. 

An orderly assembly pro 
cedure is recommended be 
cause of the cramped PC boarc 
layout and the mixture of smal 
and large components on th< 
board. Solder all surface-moun 
IC's to the board first. This is tin 
most time-consuming and te 
dious part of the project! 



Si 



z 

8 
c 
S 

I 

LU 

42 




COMPONENT SIDE of E-Comm transceiver circuit board 




WIRE SIDE of E-Comm transceiver circuit board 



In soldering SMD ICs, first tin 
one of the comer pads on the PC 
board. Then, with needle-nose 
tweezers, grasp the part and 
center it so the leads align with 
all of the pads . Solder the comer 
lead to the pad that has been 
tinned. Next solder the pin diag- 
onally across from the first pin, 
making sure that the case is still 
centered on the pads. Before 
soldering the remaining pins, 
refer to Fig. 5 and verify that the 
IC is in the correct position; 
then double check to be sure 
that pin 1 is in the correct loca- 
tion. 

Be careful not to apply too 
much solder at each pad, and 
try to avoid making inadvertant 
bridges with the molten solder 
between intended connections 
and adjacent pins. If bridging 
occurs, use a solder- re moving 
braid and flux to remove it. Also 
avoid holding the soldering 
pencil at any connection point 



for more than the time requred 
to cause the molten solder to 
flow to prevent overheating the 
component. 

The next step is to position 
and solder all SMD chip capaci- 
tors and resistors. Install all re- 
sistors and capacitors of the 
same value at the same time to 
avoid mixing values! Tin one 
pad of two-terminal compo- 
nents, place the component in 
the correct position, and hold it 
with tweezers while soldering it 
to the tinned pad. Next, solder 
the other end. 

As in soldering the ICs, use 
only as much solder as is neces- 
sary to form a fillet between the 
component and the PC board 
pad. Be sure that the compo- 
nents are positioned flush 
against the board. 

After all SMD components are 
mounted, clean the entire PC 
board with flux remover, and in- 
spect all of the soldered connec- 



tions with a magnifying glass 
all of the SMD soldering appes 
satisfactory, mount all of t 
leaded through-hole comr. 
nents with the exception of : 
ductor L8 and solder them 
position. (Inductor L8 is to 
installed after the multipli 
stages are aligned.) 

lake care when soldering t 
connectors because their lea 
are off-centered. The axial-Ies 
ed inductors and resistor Rl i 
mounted through holes. U 
the silkscreened pattern on t 
PC board as a guide. Be sure 
mount the switches and pote 
tiometers so they lie flu; 
against the PC board. 

Now assemble the batte 
pack, microphone and speak 
Assemble the connector plu 
for J3 to J5 by crimping a 
soldering them to the batte 
pack, microphone and speak 
wires. Solder two six-im 
lengths of insulated 26 AV 
wire to the speaker and tw 
them together. Next solder pi 
to the ends of the speaker win 
being careful not to let sole 
flow into contact area. Th 
push the pins into the mati 
plastic plug housing. Each p 
should snap into place if it- 
assembled correctly 

The assembly work on t 
battery pack subassembly 
limited to twisting the wir 
and attaching the connect 
plug. Note that this connectoi 
polarized and can only plug 
one way. Verify that the batte 
connector polarity is correct 1 
cause reversed polarity will c 
stroy the transceiver! 

Solder a four-inch length 
shielded coaxial cable to the n 
crophone with the shield cc 
nected to the negative side 
the microphone. Then conn( 
the cable to the polarized cc 
nector, again observing polari 

Fasten the microphone ir 
the plastic snap-in bushi: 
with a room-temperature w 
canizing (RTV) silicone adr 
sive. Mask the front surface 
the microphone with maski 
tape to prevent the entry of a 
adhesive in the microphone 
it could be ruined. Be sure t± 
the wire side of the micropho 
is flush with the back of t 
continued on page 



BUILD THIS 

REFLEX TIMER 



£ tin 
f>Otf , 



Reflex Timer 



How fast are your reflexes? 

The reflex timer will show you. 



DAN KENNEDY 



HOW LONG DOES IT TAKE YOU TO 

close a switch after you hear a 
buzzer? When driving, how 
long does it take to hit the 
brakes after you see an obsta- 
cle? What we're really asking is, 
"How quick are your reflexes?" 
Our reflex timer will show you. 

Testing your reflexes is a two- 
person job. To use it, one person 
secretly starts the timer, which 
sounds a buzzer. Upon hearing 
the buzzer, the person whose re- 
flexes are being tested turns the 
timer off as fast as he can. (That 
also turns off the buzzer.) The 
person's reflex time can then be 
determined by observing a 10- 
LED display. 

Figure 1 Is a schematic di- 
agram of the reflex timer, which 
consists of a 555 timer (IC1) and 
three 74LS193 4-bit binary 
counters (IC4-IC6). The 555 
timer outputs a pulse about 
twice every millisecond, or 2000 
times a second. The timer is se- 



cretly activated by SI which 
then turns on piezo buzzer BZ1 
via Ql, and connects the clock 
output from the 555 to the bin- 
ary counters through one nand 
gate (IC3-d), as shown in Fig. 2. 
The person being timed turns 
S2 off, which disconnects the 
555 output from the counters 
and turns off the buzzer. Quad 
nand gate IC2 is configured as 
two separate latches, also as 
shown in Fig. 2, to prevent the 
contacts of SI and S2 from 
bouncing. 

Depending on how long it 
takes the person to shut off the 
timer, a certain number of 
LED's light up. The numbers 
next to each illuminated LED (1, 
2, 4, 8, 16, 32, etc.) are then 
added together to give the per- 
son's reflex time in millisec- 
onds. If all the LED's are lit, the 
total elapsed time is 511 millise- 
conds or 0.511 seconds. The in- 
dicated time can be multiplied 



by a correction factor to give ; 
more precise measurement, bu 
that's not necessary for relativ 
measurements or "contests"ti 
determine who has the fastes 
reflexes. We'll talk more abou 
the correction factor later. 

A 7805 voltage regulator (IC7 
provides + 5-volts DC for the cii 
cuit from a 9-volt battery. Tw 
5. IK resistors (Rl and R2) and 
0.047 jxF capacitor (CI) give tb 
555 a clock frequency of approj 
imately 2000 Hz, or 2 cycles p< 
millisecond. Try using a few di 
ferent 0.047-^F capacitors ft 
CI to get the frequency as clos 
to 200 Hz as possible. Closir 
switch S4 puts C2 (a 47 |j.F c 
pacitor) in parallel with C 
That slows down the timer 
demonstrate how a binai 
counter works. The numben 
LED's will count the number 
times that LED1 turns on. Tl 
formula 1440/(R1 + 2R2)( 
gives the timer frequency in H 




LEDS 
18) 



©- 






RIO 
470J1 



LE07 
(321 



& 



LED6 470n 
(16) 



R11 
470O 



-VA- 



^ 



^ 



@" 



R12 
47fl« 



%- 



LEDB 

(64> +5V-" 



R16 
IK 



LED9 
(125) 



^ 



LED10 
(256) 



R14 
47011 



-^r 



R13 
470n 



R1S 
470a 



1 

=• 2 



P1 

Q1 
QO 
ON, 

UP, 

02 

Q3 
GND 



•cc 
PO 

IC4 CL 
74LS193 DN 

UPo 
LD 

P2 
P3 



+ 5V 



21 

15 

13 * 
12 



+5V 



11 



10 



pi 

Q1 
QO 
DN, 

UP, 
02 
03 

end 



pi 

CL 
74LS193 DN o 



0^ 



UP 
LD 
P2 
P3 



+5V 



13_ ■= 
II 



n 
4 



- 2 



-WS- 



_L LED11 
- (1024) 



8 



r-l 



IT-H-^ 



IC7 

78Q5 



P1 

Q1 
QO 
DN, 

UP, 
Q2 
Q3 

GNO 



IC6 
74LS193 



PO 

CL 

DN,,, 

UPo 
LD 
P2 
P3 



+5V 
16_J 



|5 
14 

13_ - 

12. 

n 



C1 
.047 



R4 
4.7K 



$4 
CLK 



C2 
47jiF 



+ 5V 



IC1 
555 



+5V Hi 
ft t 51K 



. ; 82 
:-5.1K 



On 



? 



o 
Ir 9 



Z>] 



rOza 



Eh 



*v c 



GND IC2 
74LS00 



+ 5V 
14j 

13 



10 



-^^tDi 



m^ 



t +5V 
OUT 




££> 



+ 5V 



+ 5V 




FIG. 1— SCHEMATIC OF THE REFLEX TIMER. It consists of a 555 timer and three 

74LS193 4-bit binary counters. 






a 
i 



s 

J) 

111 



44 




1 M 13 V. 74LS00k> iiJ 



S5 
BUZZER OHfOH 



FIG. 2 — QUAD NAND GATE IC2 is configured as two separate latches to prevent the 
contacts of S1 and S2 from bouncing. The clock output from the 555 is connected to 
the binary counters through one gate of IC3. 



when Rl and R2 are in kilohi 
and CI is in microfarad 
Switch S5 lets you turn off t 
buzzer when demonstrating t 
counters with the lower clo 
speed. 

The 74LS193 counters 

The 74LS193 is a 4-bit u 
down binary counter that a 
operate at clock speeds up to i 
MHz. Data input pins po- 
allow a 4-bit binary number 
be loaded into the counter b 
fore counting begins. The loj 
input (ld, pin 11) must 1 
pulsed low to load the 4-b 
number. Notice that the data i 
puts (po-P3) of all three counte 
are grounded and that the loj 
pins are held at +5 vol 
through R4. Momentarily clc 



10 



12 



13 



14 



Q0{1) 1 





1 





1 


. 


1 





1 





1 





1 





CW21 


1 


1 








1 


1 








1 


1 








1 


Q2W 








1 


1 


1 


1 














1 


1 


1 


Q3(8) 


D 

















1 


1 


1 


I 


1 


1 


1 



15 


16 


17 


ETC. 


1 





1 




1 










1 











FIG. 3— WHEN ONE COUNTER FINISHES counting up to 15, it sends a carry pulse to 
the next counter. Here's how a counter responds to 17 clock cycles. 



SV 



ov 






T< 



[.5ms PER CYCLE) 



FIG. 4 — THE COUNTERS ADVANCE one count on each low-to-high transition of the 
clock (point "X" on each rising edge). 




FIG. 5— THE REFLEX TIMER PROTOTYPE was built using perforated construction 
board and point-to-point wiring. Switches S1 and S2 are housed In plastic 35mm film 
canisters and connected to the main board with three-connector wire. 



ing switch S6 grounds the ld 
pins and sets all three counters 
to zero. Although the clear 
inputs (cl) are permanently 
grounded, pulsing them to +5 
volts would also reset the cir- 
cuit's counters. 

The count down inputs {dn,, 
pin 4) are held at +5 volts 
through R16. The clock signal 
from pin 3 of the 555 is applied 
to pin 5 on the first counter, IC4. 



When IC4 finishes counting up 
to 15, it sends a carry pulse from 
its up (pin 12) to the count up 
input (up,, pin 5) of the second 
counter, IC5. Likewise, when 
the second counter reaches a 
count of 15, it sends a carry 
pulse from it up pin to the third 
counter, IC6. Figure 3 shows 
how a counter responds to 17 
clock cycles. A low-to-high tran- 
sition triggers the counter. 



When a counter reaches 15, it 

starts counting again at zero. 

Accuracy 

Figure 4 shows the clock sig- 
nal that is fed to the counters, 
which advance one count on 
each low- to-high transition of 
the clock (point "X" on each ris- 
ing edge). We can start and stop 
the count anywhere in the clock 
cycle. Suppose we start at T, 
(just after a low-to-high transi- 
tion) ; the timer will advance one 
count when T 2 is reached, 
which will correctly indicate 0.5 
milliseconds have elapsed. 
However, we don't know exactiy 
where in the clock cycle the 
timer will be started. Suppose 
the timer is started at T 2 and 
stopped at T 3 . The timer would 
read 0.5 milliseconds more 
than the actual elapsed time be- 
cause the timer started at T 2 
and immediately registered one 
count. 

A similar situation occurs at 
the stop time. If we start the 
timer at T t and stop at T 3 the 
count will be correct. But if we 
start the timer at Tj and stop at 
T 4 , the timer would read 0.5 
milliseconds less than the actu- 
al elapsed time since we stopped 
the counters just before a low- 
to-high transition. That means 
that the accuracy of our timer is 
limited to ±0,5 milliseconds 
when we use a 2000-Hz clock. 
(That is also plus or minus the 
least significant bit (LSB) of oui 
counters, which is the LEE 
without a number next to it. 

Another factor that deter 
mines the accuracy of the refle: 
timer is the clock frequency. I 
you have a frequency counte: 
you can measure the clock out 
put from IC1 direcUy. If a fre 
quency counter is not available 
you can measure the clock fre 
quency using a stopwatch ant 



PARTS LIST 

All resistors are Vi-watt, 5%, 

R1, R2— 5100 ohms 

R3— 10,000 ohms 

R4— 4700 Ohms 

R5-R15 — 470 ohms 

R16— 1000 ohms 

Capacitors 

CI — 0.047 fj.F, ceramic 

C2— 47 fiF, 10 volts, electrolytic 

Semiconductors 

IC1— 555 timer 

IC2, IC3— 74LS00 quad NAND 
gate 

IC4-IC6— 74LS193 4-bit binary 
counter 

IC7— LM7805 5-volt regulator 

Q1— 2N3904 NPN transistor 

LED1— LED10— red LED 

LED11— yeiiow LED 

Other components 

6Z1 — Piezo buzzer 

SI, S2— SPDT switch with center 
Off 

S3-S5— SPST switch 

S6 — SPST normally-open push- 
button switch 

Miscellaneous: Perforated con- 
struction board, standoffs, project 
case, IC sockets, wire, solder, etc. 



the calibration LED (LED11). If 
the clock frequency is exactly 
2000 Hz, then it would take 
40.96 seconds for LED 11 to 
turn on twenty times. The au- 
thor measured 41.5 seconds for 
LED11 to light twenty times. To 
calculate the frequency, multi- 
ply 2000 x 40.96/41.5; that 
comes to 1974 Hz. (A frequency 
counter measured it at 1979 
Hz.) With a clock frequency of 
less than 2000 Hz, the indicated 
reflex time would be slightly less 
than the actual reflex time. Mul- 
tiplying the indicated time by a 
factor of 2000/1974, which is 
equal to 1.013, would give the 
reflex time correct to the nearest 
millisecond. 

Construction 

No PC board is required to 
build the reflex timer. Instead 
you can use perforated con- 
struction board and point-to- 
point wiring. The photo in Fig. 
5 shows how the authors pro- 
totype was built and installed in 
a plastic case. 



The author used plas 
35mm film canisters to hoi. 
switches SI and S2, althou 
other mounting schemes c 
certainly be used. Three-cc 
ductor wire must be used 
connect SI and S2 to the tru 
board. 

It's a good idea to mount t 
IC's in sockets. That way y 
can easily exchange t 
74LS193'swith 74LS192'sto« 
how a decade counter worl 
The 74LS192 has the same p; 
out as the 74LS193 but cour 
only to nine before generating 
carry pulse and repeatin 
Using those chips, the tim 
would display up to 399/2 
199.5 in binary-coded decirr 
(BCD), If you wanted to read t 
time directly in millisecond 
(from BCD) you would have 
change the clock frequency 
1000 Hz. 

The reflex timer is sure to bt 
smash hit at your next party 
with it, you will be able to see 1 
yourself who has the absolu 
fastest reflexes. F 



fi! 



! 



£ 
1 

ID 



46 



Train at HOME to be an 

Electronics Technician I 





As the demand for computers and microprocessors 
in business, manufacturing and communications 
continues to grow, so does the need (or qualified 
technicians. It's not unusual for experienced 
technicians to earn from $30,000 to more than 
$40,000 a year.* Now through Peoples College 
of Independent Studies you can train for this 
exciting field without interrupting your job or 
home life. 



Choose From Five Prog rami oi Study f^ 



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•Specialized Associate Degree In Electronics 
Technology 



Depending on the program you select, you'll 
perfect your skills using this advanced equipment, 

included in the price of tuition: 

• IBM-Compatible Personal Computer 

• Digital Multimeter 

• Digital Logic Probe 

• Elenco Oscilloscope 

• Portable Cellular Telephone 

l* Source: U.S. Bureau of tjtxw SutnlKth 






Exclusive I 
That Enhance Your Training 

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• Accelerated Learning System — a scientifically 
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• Experience Labs — professionally designed 
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experience. 

• Industry Certification Training Guide — provided 
with four of our programs Prepares you for 
examinations you may take for your professional 
license or certification. 



sy Payment Plan* — No Finance 



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OF INDEPENDENT STUDIES 
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Mmibw, 0,1. P»pl« Cioop R 1 092 



CIRCLE 1M ON FREE INFORMATION CARD 



THIS MONTH WE CONTINUE 

our PC -based test-equip- 
ment series by building 
the T1004 digital logic IC 
tester and identifier. It is 
capable of testing 7400. 
5400, and 4000 series 
ICs. In fact, the T1004 
should be able to test any- 
digital IC family that has 
the standard V cc (+5V) 
and ground configura- 
tion (V cc on the upper 
left corner of the IC pack- 
age and ground on the 
lower right). On a 14-pin 
DIP that would mean that 
V cc would be pin 14 and 
ground would be pin 7. 
The T1004 will accept 
14-. 16-, 18-. 20-, 22-, and 
24-pin DIP'S. 

The T1004 performs 
the foil owing tests: Truth 
table, positive-going in- 
put threshold, negative- 
going input threshold, 
input hysteresis, output 
source capability under 
load, and an open-collec- 
tor test. Additionally, the 
T1004 predicts (based on 
a best-guess analysis) 
what type of IC you are 
testing (HC, HCT, TTL. 
etc.). From now on, you'll 
find grab bags of un- 
known ICs very appeal- 
ing because the T1004 
has a feature that can 
help you identify those 
unknown digital ICs. If 
the IC being tested 
matches any of the ICs al- 
ready in the IC database, 
the T1004 will find and 
display the names of 
those ICs. Running a complete 
test on one or all of those names 
will, in many cases, provide you 
with a comprehensive picture of 
the IC under test. The T1004 
also lets you add ICs to the 
database. As we expand our IC 
support library we will make up- 
dated files available on the RE- 
BBS (515-293-2283. 

1200/2400. 8N1). 

General operation 

Figure 1 shows the T1004 
block diagram. The chip-select 
section is driven by the Front 
End section which we dis- 
cussed in detail in our June 



PC-BASED 
TEST BENCH 




The T1004 digital logic IC 

tester and identifier can 

handle 7400-, 5400-, and 

4000-series ICs. 



STEVE WOLFE 



1992 issue; it selects and de- 
selects every other section in 
the T1004. The reference-volt- 
age section provides a 2.5-volt 
reference for the analog-to-dig- 
ital converter (ADC) section and 
also for the digital-to-analog 
converter (DAC) section. The 
pull-up or pull-down section 
(PUPD) is capable of providing a 
10-kilohm pull-up or a 200-ohm 
pull-down to any or all of the 
test-socket pins (except the V cc 
pin). 

The DAC section produces a 
voltage (in 20-milHvolt steps be- 
tween and 5 volts) which is fed 
to the DAC multiplexer (MUX) 



section. The DAC MUX 
can apply the DAC voltage 
to one of pins 1 through 
23 of the zero insertion 
force (ZIF) test socket. 
The DAC multiplexer can 
also disconnect the DAC 
voltage from the test 
socket. The ADC multi- 
plexer can select a single 
voltage from one of pins 1 
through 24 of the test 
socket and feed that volt- 
age to the input of the 
ADC section. The socket- 
ground section supplies 
ground to one of six test- 
socket pins (pins 7-12) to 
connect the ground pin of 
the IC under test to 
ground. 

Tests performed 

• Truth-table test 

During this descrip- 
tion we'll use a 7432 quad 
2-input or gate as an ex- 
ample device. Because 
the 7432 is a 14-pin de- 
vice, the socket-ground 
section grounds pin 7 of 
the test socket. The DAC 
section is disconnected 
from the socket. The de- 
vice is looked up in the 
database and an input/ 
output (I/O) mask is 
stored as three variables 
(or three 8-bit bytes). The 
I/O mask differentiates 
inputs from outputs. 
During subsequent test- 
ing, the I/O mask protects 
outputs from being inad- 
vertently grounded. Next, 
a line of the truth table is 
read into the three variables 
from the data base. The 
portions of those three variables 
which correspond to inputs are 
sent to the IC under test via the 
PUPD section. 

At this point the ADC multi- 
plexer and ADC sections scan 
every test socket pin for the re- 
sultant voltage. Voltages found 
to be greater than 2.4 volts are 
converted to highs, and those 
less than 2.4 volts are converted 
to lows. The highs and lows are 
converted to three 8-bit bytes 
that are compared to the bytes 
that were read in from the truth 
table. If they match, the IC has 



TO OAC SECTIDN 



S! 
I 

| 



I 

z 



s 

1 

4a 




TO THE 

FRONT 

END 



DATA BUS 



TO 

EVERY 

SECTION 




PULL UP OR 
PULL DOWN 



DM MUX 






T0 23ZIF- 
SOCKETP1NS 



TO ONE OF 23 

Ztf-SOCKET 

PINS 



DAC 



ADC MUX 



j^^" 



f ROM ONE OF 24 

ZIF-SOCKFT 

PtNS 



ADC 




SOCKET GROUND 



{-► 



TO ZIF-SOCKET 

PIN 7.8.9,10.11. 

OR 12 



FIG, 1 — T1004 BLOCK DIAGRAM. The Front End drives the chip-select section, which 
selects and deselects every other section in the T1004. 



passed the first line of the truth 
table. 

• Low-to-high input test 

In this section three bytes are 
again sent to the test socket. 
The bytes are selected based on 
the following criteria: A known 
input pin on the IC under test is 
being held low. Additionally, 
when the pin being held low is 
taken high, a known output pin 
will change state. Working to- 
gether, the DAC and DAC multi- 
plexer sections take control of 
the input pin and slowly ramp 
its voltage from zero to the volt- 
age level needed to cause the 
output pin to toggle. The volt- 
age on the input pin is then 
read back and displayed on- 
screen next to the label "VT+ :." 

• High-to-low input test 

In this section three bytes are 
again sent to the test socket. 
The bytes are selected based on 
the following criteria: A known 
input pin on the IC under test is 
being held high. Additionally, 
when the pin being held high is 
taken low, a known output pin 
will change state. The DAC and 
DAC multiplexer sections take 
control of the input pin and 
slowly ramp its voltage from + 5 
volts to the voltage level needed 
to cause the output pin to tog- 



gle. The voltage on the input pin 
is then read back and displayed 
next to the label "VT- :." 

• Hysteresis 

Input hysteresis is the dif- 
ference between the trigger 
point of an input being taken 
high and the trigger point of the 
same input when it is taken low, 
IC's such as a 7414 intentionally 
have a large amount of hys- 
teresis to give them increased 
noise immunity. The T1004 cal- 
culates the hysteresis and dis- 
plays it on the screen next to the 
label "HYS:." The T1004 calcu- 
lates hysteresis as follows: 
(VT+) - (VT-) = [Hysteresis) 

• TTL input compatibility 

A TTL-compatible input must 
trigger when fed a voltage not 
larger than 2.4 volts. If VT+ is 
greater than 2.4 volts then the 
IC under test fails the test. 

• Output-load test 

The output- load test is per- 
formed by taking an output 
high and loading it with 200 
ohms to ground for a very brief 
period. During the time that the 
load is present, the ADC reads 
the loaded voltage. This test will 
reveal weak or damaged gates, 
help to identify the gate type, 
and test for an open-collector 
condition. 



Any of the tests describ 
above may be omitted from I 
testing procedure. The testi 
process is defined by a scri 
which is a set of test instn 
tions for a particular IC. Ea 
IC has its own script which TJ 
or the end user writes to sui 
particular IC. IC scripts i 
compiled using a program si 
plied by TSW. 

Script tutorial 

IC's not presently support 
by the T1004 can be added 
the existing database by t 
user. Each script contains 1 
IC's name, whether the IC is 
open-collector device, and 
truth-table informatio 
Scripts can be written usi 
any ASCII text editor. 

The easiest way to creab 
new script is to copy an existi 
script and edit it as needi 
Once a script has been creati 
it can be compiled and added 
the appropriate database. \ 
can compile a script simply 
selecting that option from i 
software menu. You will 
asked to give the name of 1 
script (example: S7400.TS1 
The compiler will then open i 
script and get the IC nan 
Next, it checks to see if the t 
get IC already exists in t 
database. If it already exis 
then the previous version of t 
IC script will not be overwrittt 

The delete function lets y 
remove any IC from t] 
database. If the target IC dc 
not exist in the database, th 
the compiler will compile t 
target script file and add the 
suits to the database. The ori 
nal script is written in a foi 
that is easy for a person to f 
low. Once compiled, the scri 
takes on a more compact foi 
that can be used by the ma 
testing program. Scripts for 1 
pin IC's must be located in t 
directory "\TSW\ICTES 
\D14\SCRIPTS." Similar 
scripts for 20-pin IC's must 
located in the directo 
"\TSW\ICTEST\D20\SCRIPTS 
and so on. 

Take a look at Listing 1. T 
top line (TUTORIAL SCRI 
NUMBER 1) and the numbt 
down the left side (1-14) are r 
part of the script file. They hs 



been added for reference only, 
and should not appear in 
scripts that you write. 

The symbols in the beginning 
of each line tell the software 
what kind of function is to be 
performed. A "?" tells the soft- 
ware that the two following vari- 
ables are the IC's name and 
whether or not it is an open- 
collector device, respectively. A 
"#" tells the software that the 
letters "I,""0,""V," and"G" des- 
ignate inputs, outputs, V cc , 
and ground, respectively. "V" 
and "G" always represent V cc 
and ground, respectively. The 
numbers "1" and "0" always rep- 
resent a logic high and a logic 
low, respectively. 

An "*" tells the software that 
following symbols designate the 
truth table of the IC under test, 
and that the data should be sent 
and the results should be read 
back. A "%" indicates that the 
following symbols designate the 
truth table of the IC under test, 
and that the data should be sent 
but not read back. A 7" tells the 
software that the following sym- 
bols designate the truth table 
used for the "low-to-high input 
threshold test" of the IC under 
test. A "!" says that the two 
following numeric variables 
designate the "low-to-high in- 
put threshold test" input and 
output pins, respectively. A "\" 
indicates that the following 
symbols designate the truth ta- 
ble used for the "high-to-low in- 
put threshold test" of the IC 
under test. A "-" means that the 
following symbols designate the 
truth table used for the "output 
load test" of the IC under test. 
An " = " means that the follow- 
ing numeric variable designates 
the "output load test" output 
pin. 

Let's take a closer look at the 
script in Listing 1. Line (1) must 
contain three string variables 
separated by commas. The first 
variable in the line must be a "?" 
which tells the software that the 
next character is the name of 
the IC. The IC name can contain 
nine characters. In this case the 
name is "7400." The next 
character on line (1) tells the 
software whether or not the IC 
being tested is an open-collector 
part; "Y" for open-collector parts 



or "N" for parts without an open Line (4) begins with an "*." 

collector. That means that any "l"s and 

Line (2) represents the pin "0"s corresponding to inputs 

numbers of the IC being should be sent to the IC and 

scripted. In this case the IC is a that the "l"s and "O's corre- 

14-pin package. Line (3) is the sponding to outputs should be 

first line of the truth-table sec- read back from the IC. If the'T's 

tion. From that line the test and "O's read back do not match 

software is able to determine the those predicted by the script 

whether to treat any given pin then a fail condition exists. A 

as an input or as an output. The 7400 is a quad 2-input nand 

line must be correct for the lines gate. The line tests all four gates 

that follow to work correctly. If at the same time. In line (4), 

the IC being scripted has more pins 1, 2. 4, 5, 9, 10, 12, and 13 

than one input/output mode (a are all taken low. Each function- 
ing nand gate must respond by 
outputting a high. The results 

LISTING 1 are read back and compared to 

TUTORIAL SCRIPT NUMBER 1 the script. (Any error within the 

script will cause good IC's to fail 

ic name the test). Lines (5) through (7) 

ID ?'ilao'v " " send and test the remaining 

truth-table conditions. An"»" 

"piiTNOMBEHs" can be used only in the truth- 

table section. Within that sec- 

(2) 00000000011111 *.„ 

123*567890123* tion, you can use as many "*•• 

lines as you like. 

kain'troth'tmle Line (8) begins with a "7. T1 

rrTTriTrrrrnTrVr" That character causes the "low- 

(*J J;o;5:?:!:o;?:g:?:!;o;?:o:o:t to-high input test- {lhd to be 

'ill t'?'H'?'H'?'i'?'H'? r iv^ performed. The LHT is used tc 

(6) *, 1, 0, 1,1, 0,1,G,1, 1,0, 1,1,0,V *, , . ., ,,. ^ ,. 

(7) *,i,i,o,i,i,o,g,o,i,i,o,i,i,v determine the volt-age that an 

input considers a high, or log- 
low kj bigh stupor tbst ic-1. The "l"s and "0"s corre- 
ct ^iXriXi^riXiriXv" sponding to inputs are sent tc 
(9) 1,2,3 the IC. Line (9) contains tht 

character "I," which precedes 

high to low input TEST the input and output pins to be 

do) \~I~ w'l^Xo^wX™ used durin g me test - In this ex 

{ii ) 1,2,3 ample pin 2 is used as the inpu 

„ and pin 3 is used as the output 

output load test When pin 2 is taken from low tt 

(12) -Xo~iXo7iXIXo7i"oXv~~ high. Pi" 3 changes state. It i: 

(i 3 ) "-3 not important whether pin ; 

goes from high to low or low ti 

(1*) tsh electronics high, but only that a change o 

1* PIN IC TEST SCRIPT , & , J , T . nn ° . 

state occurs. The T1004 in 

creases the voltage present a 

74245, for example), you pin2(in20-millivoltsteps)unt 

should give a new "#" line just pin 3 changes states. The voll 

prior to the IC's mode change, age on pin 2 is read back an' 

You can use as many "#" lines displayed. 

as needed, and you can use Lines f 10) and (11) contain th 

them in any section of the character "\" and"!." They wor 

script. In this case pin 1 is an in the same way except that th 

input, pin 2 is an input, and pin input voltage is swept from hig 

3 is an output. Pins 4--6 follow to low. This test is used to dete 

the same pattern and pin 7 is mine VT-. Line (12) contair 

ground. Pin 8 is an output, pin the character "-." That sends 

9 is an input, and pin 10 is an truth table that must produce 

input. Pins 11-13 follow the high on one of the outputs. Th 

same pattern and pin 14 is V cc . next line contains the characti 

If you check your data book you " = ," which tells the softwai 

will see that this accurately de- which output pin is present 

scribes the I/O of a 7400. high. We could have chosen at 



95 



0) 



z 

3 

c 
2 

1 



50 



one of four outputs since they 
are all high. In this instance pin 
3 is chosen, and loaded with 
200 ohms to ground. The load 
test determines the sourcing ca- 
pabilities of the gate, whether 
the part is open-collector or not, 
and provides clues that the soft- 
ware uses to predict the IC's 
family. The prediction of family 
or type should be considered a 
best guess (not absolute). Line 
(14) contains the text "TSW 
ELECTRONICS, "which is there 
as an end-of-file marker for the 
compiler. 

Listing 2 shows "TUTORIAL 
SCRIPT NUMBER 2." Line (1) 
indicates that the device is a 
4040 and that it is not an open- 
collector device. Line (2) indi- 
cates that a 4040 is a 16-pin de- 
vice. A 4040 is a 12-bit ripple 
counter. Line (3) indicates that 
pins 1—7 are outputs, pin 8 is 
ground, pin 9 is an output, pins 
10 and 11 are inputs, pins 12—15 
are outputs, and pin 16 is V cc . 
Pin 10 is a falling- edge triggered 
clock input. Pin 11 is used to 
reset the counter, and is active 
only when high. Line (4) intro- 
duces the "%" command, which 
is similar to the •'**■ command, 
except that no test is performed; 
"%" should be used whenever 
you wish to send a byte to the IC 
without testing for a result. 

In line (4) the reset line (pin 
11] and clock line (pin 10) are 
taken high. On that same line 
all of the outputs are shown low, 
which is an accurate represen- 
tation of the effect that a reset 
would have on the outputs. Be- 
cause line (4) is a " %" line, we do 
not actually test the outputs. 
On line (5) the reset line is re- 
leased. On line (6) the clock is 
taken low activating the first 
output line (qo). Because line (6) 
uses an ■• * ■■ instead of a " % , " the 
outputs will be tested for ac- 
curacy. The "%" command al- 
lows you to configure a device 
before you begin to test it. It can 
be used in any section and as 
often as you like. In the low-to- 
high input test, it is used to rec- 
onfigure the 4040 before we 
sweep the input. In this case, 
we are using the reset input to 
determine the low-to-high 
threshold (VT+ ). 
The only pin that could be 



used for the high-to-low input 
test is the clock pin. Because 
clock input pins require fast 
transition times, they are not 
suitable for use in threshold 
tests. For that reason, the high- 
to-low input test is omitted for 
the 4040 IC. You can omit any 
section except the "?" section 
and the "TSW ELECTRONICS" 
section. A "#" must precede 
truth-table, threshold, or out- 
put-load tests. It must appear at 
least once or as often as needed. 



LISTING 2 
TUTORIAL SCRIPT NUMBER 2 





IC NAME 


(1) 


?,4040,H 




FIN NUMBERS 


(2) 


0000000001111111 




1234567B90123456 




HAM TROTH TABLE 


<3) 


*,O,O,O,O,0,O,0,G,O,I,I,O,O,0,O,V 


(*! 


», 0, 0, 0, 0, 0,0, 0,5,0,1, 1,0, o,o,o,v 


(5> 


t,0,0,0,0,0,0,0,G,0,l,0,0,0,0,0,V 


(61 


*,0,0,0,0,0,Q,0,G,1,0,0,0,0,0,0,V 


m 


«,0,0,0,0,0,0,0,G,1,1,0,0,0,0,0,V 


(8) 


*,0,0,0,0,0,0,1,G,0,0,0,0,0,0,0,V 


O) 


*,0,0,0,0,0,0,1,G,0,1,0,0,0,0,0,V 


(10) 


*,0,0,0,0,0,0,1,G,1,0,0,0,0,0,0,V 


(11) 


«,0,0,0,0,0,0,1,G,1,1,0,0,0,0,0,V 


(121 


*,o,o,o,o,o,i,o,g,o,o,o,o,o,o,o,v 


(131 


•,0,0,0,0,0,l,0,G,0,l,0,Q,0,0,O,V 


{M| 


*,o,o,o,o,o,i,o,g,i,o,o,o,o,o,o,v 


(15| 


*,0,0,0,0,0,1,0,G,1,1,0,0,0,0,0,V 


(16| 


*,o,o,o,o,o,i,i,g,q,o,o,o,o,o,o,v 


fl?l 


*, 0,0, 0,0,0, 1,1, G, 0,1,0, 0,0,0, o,v 


(16) 


«,0,0,0,0,0,I,1,G,1,Q,0,0,0,0,0,V 


(19) 


•,o,o,o,o,o,i,i,g,i,i,o,o,o,o,o,v 




lob TO HIGH input test 



(20) *,0,0,0,0,0,0,0,G,0,1,1,0,0,0,0,V 

(21) %,0,0,0,0,0,0,0,G,0,l,0,0,0,O,0,V 

(22) /,0,0,0,0,0,0,0,G,1,0,0,0,0,0,0,V 

(23) |,11,9 



OOTPtJT LOAD TEST 



(24) 1,0, 0,0, 0,0, 0,0, G, 0,1, 1.0, 0,0, Q,V 
(2S)*,O,0,0,0,0,0,0,G,0,l,0,0,0,0,0,V 
(28) -,O,0,0,0,0,0,0,G,l,0,0,0,0,0,0,V 
(27) -,? 



(2B) TSW ELECTRONICS 

16 PIH IC TEST SCRIPT 



Detailed operation 

We will use BASIC as an exam- 
ple language. As we've seen with 
previous peripherals, the first 
step in controlling the T1004 is 
to establish a base address and 
select the desired peripheral. 
The first bit of code will be: 
BAS = 768 : OUTBAS + 31,4 
768 (hex 300) is the factory-pre- 
set base address of the 1 1000. As 
noted earlier, this address is 



DIP-switch selectable. Next, ^ 
have an "OUT TO BAS + 31." i 
you may recall, that address 
reserved for peripheral sele 
tion. The T1004 has a unit, 
peripheral address of "4." Co 
sequently, if we send an "Ol 
TO BAS + 31" with a data byte 
"4," the T1004 will be readii 
for full I/O operation. 

The T1004 schematic h 
been split into two halves ai 
shown in Figs. 2 and 3. Addre 
lines AO-A4 (32 bytes) are us 
by the T1004 (or any other r. 
ripheral) to address its IC's, ar 
ao is the LSB of the addre 
lines. (Lines ab-as are used 
the 1 1000 only.) The chip-sek 
section shown in Fig. 
(IC23-IC25) contains t\ 
74HCT138's (IC23 and IC2^ 
Whenever their G2A and g 
lines are low and gi is high, oi 
of eight outputs will go low c 
pending on the address prese 
on the a, b. and c inputs. IC23 
active when ben is high, send 
low, and rd is low. IC24 is acti 
when ben is high, send is lo 
and wr is low. All but one 
IC24s output lines drive tl 
load line of the 74HCT5: 
latches. Because the load line 
a 74HCT573 must see a high 
store data, IC25 inverts the a 
tive lows produced by IC24. 

The voltage- re fere nee sectio: 
also in Fig. 2, is composed 
IC26. R21, Rl, IC9-a. and IC9- 
Trimmer R21 is adjusted for 2 
volts at TP1. That provides tl 
ADC section with a precise re 
erence voltage. The referent 
voltage also passes through IC 
b and used by the DAC sectio: 

An "OUT TO BAS + 7" will lo* 
a data byte into IC15 (a later 
DAC IC16, in combination wii 
IC17-a, will produce between 
and 5 volts which is propc 
tional to the byte stored in IC1 
The voltage produced will be 
function of n x (5/255), where 
is equal to the number load* 
into the latch (IC15). A 500-oh 
potentiometer (R22) is used 
set the full-scale output voltag 
If IC15 contains a value of 25 
then R22 should be adjusted fi 
5 volts at IC17-a pin 1. The DA 
multiplexer section is con 
posed of IC18 through IC22. 
latch (IC18) used to hold tl 
DAC multiplexer address. Tl 









tea 








7IUB 








1 s 


a 


,. 


i. 


137 


1 


c 


8* 


100) iF 




!0Mf | 










- 


r 







FIG. 2— IN THIS PORTION of the T1004 schematic, address lines A0-A4 are used to 
address IC's. 



least significant three bits of the 
address are fed to each of three 
8-bit multiplexers 

(74HCT4051). The remaining 
data lines are fed to IC19 (a 



74HCT138), which activates 
only one of the multiplexer IC's 
(IC20-IC22). Assuming that the 
address byte sent to IC18 was 
less than 23, the DAC voltage is 



then passed through to the tes 
socket. If the address byte is 2: 
or greater, then the DAC voltag 
is disconnected from the tes 
socket. 




Jii-iiiiiiiijji 



FIG. 3— THE PULL UP OR PULL DOWN section pulls any or all of the test socket pins 
52 high or low as needed. 



Latch IC10 is used to hold tl 
ADC multiplexer address. Tl 
least-significant three bits 
the address are fed to each 
three 8-bit multiplexers. The r 
maining data lines are fed 
IC11. a 74HCT138, which act 
vates only one of the multiplex! 
IC's (IC12-1C14). Assuming th; 
the address byte sent to IC1 
was less than 24, the ADC r 
ceives voltage from only one 
the test socket pins. If the a< 
dress byte is 24 or greater, the 
the ADC is disconnected fro: 
the test socket. 

The pull up or pull dow 
(PUPD} section, shown in Fig. ; 
is composed of 1C1, 1C5, IO 
RIO, Rll, R13-R16, R17-R1! 
Q1-Q8, and Q15-Q29. This se 
tion pulls any or all of the te. 
socket pins high or low £ 
needed. The PUPD section 
primarily responsible for trutl 
table functions. Three bytes a: 
used to control the PUPD se 
tion, Byte-A controls test sock 
pins 1-8, Byte-B controls pir 
9—16, and Byte-C controls pir 
17-23. Pin 24 is reserved f< 
V cc only and is not affected t 
the PUPD or DAC sections. Tl 
sections controlled by Byte-,/ 
Byte-B, and Byte-C are fun 
tionally identical, so we'll d 
scribe the Byte-A section only. 

We'll assume that the nurabi 
85 (01010101) has been sent i 
IC1. The output enable line c 
IC1 (oe) is grounded so the "£ 
outputs must follow the "D" ii 
puts. Pin 1 of DIP RIO will r 
ceive a high, pin 2 a low. pin 3 
high, and so on. Resultantl 
the base of Ql will be taken hig 
connecting ground to Rll pin 
That causes pin 1 of the te! 
socket to be pulled low throug 
200 ohms. Because the base * 
Q2 is low, it will not conduc 
That allows R17 pin 3 to pull R: 
pin 2, and subsequently the te: 
socket pin 2, high. 

The IC ground section coi 
sists of IC2-IC4, R12, an 
Q9-Q14. Any byte latched ini 
IC2 is passed directly to IC; 
Byte values ranging from to 
transition to a low one of IC3 
output lines. IC4 Inverts tf 
signals which are then fe 
through R12 to the bases < 
Q9-Q14. Only one line is acth 
at a time, thus ensuring th; 



only one transistor is con- 
ducting at any given moment. 
Transistor Q9 is selected when 
driving a 14-pin device and Q14 
would be used when driving a 
24-pin device. 

Regulator IC27 and Its associ- 
ated components produce -5 
volts, which is used by the DAC 
(IC16). Regulator 1C28 and its 
associated components pro- 
duce - 5 volts for the multiplex- 
ers (IC12-IC14 and IC20-IC22). 
Regulator IC29 and its associ- 
ated components produce + 7 
volts, which the op-amps re- 
quire in order to produce a full 
5-volt output swing. Regulator 
IC31 and its associated compo- 
nents produce + 5 volts for the 
IC being tested. Regulator IC30 
and IC32 and their associated 



components produce +5 volts 
for all the remaining IC's. Reg- 
ulator IC31 produces +5 volts 
and is dedicated to supplying 
V cc to the test socket and +5 
volts to the pull-up resistors 
R17-R19. 

Construction 

To build the T1004 pe- 
ripheral, a PC board is recom- 
mended. You can either buy a 
PC board from the source men- 
tioned in the Parts List or make 
your own from the foil patterns 
we've provided. Note that the 
parts for the Front End are con- 
tained on the T1004 board 
shown with a dark line around 
them in the Parts -Placement di- 
agram of Fig. 4. There is a sepa- 
rate Parts List for the Front 



End, which was discussed in 
detail in the June issue. Do not 
confuse the two lists of parts, or 
where they go on the board. 
Also, for many of the capacitors, 
notice that there are three holes 
on the board, with two of them 
electrically the same. The holes 
accommodate capacitors with 
different lead spacing. Use 
whichever pair of holes on the 
printed-circuit board that best 
fits the capacitors you intend to 
use for the project. 

One of the voltage regulators 
(IC32) is in a TO-3 case that 
must be mounted on the back 
panel of the T1004 case. Mount 
the regulator, along with an ap- 
propriate heatsink, on the back 
panel and hardwire it to the 
board. Figure 5 shows the com- 




TOZIF SOCKET PINS 
FIG. 4— PARTS-PLACEMENT DIAGRAM. The parts for the Front End are shown with a 
dark line around them. There is a separate Parts List for the Front End, so don't 
confuse the two lists of parts, or where they go on the board. 



TO ZIF SOCKET PINS 




-6"/i6 INCHES- 



-H h>- 



-6"/is INCHES- 



T1004 COMPONENT SIDE. 


T1004 SOLDER SID 




T1004 PARTS LIST 

f . 




All resistors are V4- watt, 5%, unless 


C29— 2.2 jlF, electrolytic 




otherwise noted. 


C30— 36 pF, mica 




R1— 2200 ohms 


Semiconductors 




R2— 10,000 ohms 


IC1, IC2, IC5. IC6, IC7, IC10, IC15, 




R3— 2320 ohms. 1% 


IC18—74HCT573 octal latch 




R4 — 1000 ohms 


IC3, IC11, IC19, IC23, IC24— 74HCT138 




R5— 5110 ohms, 1% 


demultiplexer 




R6— 2050 ohms, 1% 


IC4, IC25— 74HCT540 octal butter 




RS— 1100 ohms 


IC8— ADC0803 8-bil A/D converter 




R9— 240 ohms 


1C9— LM358 dual op-amp 




R10, R12, R13, R15— 1000 ohms, 16-pin 


IC12-IC14, IC20-IC22— 74HCT4051 8- 




DIP 


bit multiplexer 




R11, R14, R16— 200 ohms, 16-pin DIP 


IC16— DAC08O0 or DAC08 D/A 




R17-R20— 10,000 ohms, 10-pin SIP 


converter 




R21— 10,000 ohms, muliitum trimmer 


1C17— LM6218AN op-amp 




potentiometer 


IC2&— LM336 voltage reference 




R22— 500 ohms, multiturn trimmer 


IC27, IC28— 79L05 voltage regulator 




potentiometer 


1C29— LM317T voltage regulator 




Capacitors 


IC30, IC31— LM7805T voltage regulator 


§! 


C1-C7, C10-C14, C18-C25, C48— 0,15 


IC32— UA7805K voltage regulator 


22 


jiF, polystyrene 


(TO-3 case) 


is 


C8, C16, C31, C35, C37, C39. C42, 


D1— 1N4002 diode 


& 


C45-— 100 |iF, electrolytic 


D2 1N5231 5.1 -volt Zener diode 


% 


C9, C15, C28, C32, C33, C34— not 


Q1-Q29— PN2222 NPN transistor 


O 


used 


Miscellaneous: 24-pin ZIF socket, 


i 


C17, C27, C36, C38, C40, C41, C43, 


TD-220 heatsink, TO-3 heatsink, PC 




C44, C46, C47— 10 p.F. electrolytic 


board, instnjment case, wire, solder, 
etc. 


8 


C26— 150 pF, mica 




54 



pleted T1004 board. When you 
use the T1004, position the IC's 
you want to test as shown in 
Fig. 6. 



Software 

Each peripheral has its own 
software program to control its 
operation. All of the programs 



FIG. 5— THE COM PLETED T1004. One. 
the voltage regulators, IC32, must t 
mounted on the back panel of the T10( 
case. 

end up in one directory as yc 
add more peripherals. Softwai 
for the 1 1000 and the entire s 
ries of peripherals, includir 
the T1004, can be downloads 
from the RE-BB 

(516-293-2283, 1200/240( 
8N1) as a self-unarchiving zi 
file called T1004.EXE. Bot 
compiled and uncompiled sol 
ware is included. Software is h 
eluded free with the purchase i 
any peripheral from the soun 
that is mentioned in the Par 



THE TtWM ALWAYS CONNECTS 
V M (+5 VOLTS DC) TO THIS PIN. 




PIN 1 (OF THE INTEGRATED 

CIRCUIT BEING TESTED} MUST 

BE LOCATED HERE. 




jjjjjjjii.ni 
Minor 



CORRECT POSITIONING 




INCORRECT POSITIONING 



FIG. 6— BE SURE TO POSITION the IC's you want to test in the test socket as shown 
here. 



FRONT-END PARTS LIST 


Resistors 


• 6-foot interface cable (DB-25-6)— 


R1 — 33 ohms, 16-pin DIP resistor 


$12.95 


R2— 2200 ohms, 10-pin SIP resistor 


• T1001 kit (includes PC board, all 


R3— 1000 ohms, 10-pin SIP resistor 


listed parts, project case, and pre- 


Capacitors 


assembled front and rear panels— 


C1-C7— 0.15 u.F, 50 volts, monolythicor 


$149.00 


polystyrene 


• T1001 PC board only— $49.00 


C8-C11, C20-C28— 1500 pF, 63 volts, 


• T1001. assembled and tested— 


polystyrene 


$179.00 


C12-C19— 220 pF. 100 volts, ceramic 


• T1001 software (included free with 


disc 


T1001 order)— $10.00 


Semiconductors 


• Capacitor kit (unmeasured)— 


IC1— 74LS573D octal latch 


$21.00 


IC2— 74LS688D 8-bit magnitude com- 


• Capacitor kit (measured to within 


parator 


1%)— $26.00 


IC3— 74LS245D octal transceiver 


• T1003 kit (includes PC board, all 


IC4— 74LS02D quad 2-input NOR gate 


listed parts, project case, and pro- 


IC5, IC6— octal buffer 


assembled front and rear panels) — 


IC7— 74LS08D quad 2-input AND gate 


$159.00 


Other components 


• T1003 PC board only— $59.00 


J1 — 16-pin male header 


• T1003, assembled and tested— 


J2— 18-pin male header 


$189.00 


J3— male PC-mount DB25 connector 


• T1003 software (included tree with 




T1003 order)— $10.00 


Miscellaneous: 17 shorting blocks (for 


• T1004 kit (includes PC board, all 


J1 and J2) 


listed parts, project case, and p re- 




assembled front and rear panels) — 


Note: The following items are avail- 


$209.00 


able from TSW Electronics Corp., 


• T1004 PC board only— $79.00 


2756 N. University Drive. Suite 168, 


• T1004, assembled and tested — 


Sunrise, FL 33322 (305) 748-3367: 


$249.00 


• I1000 kit— $65.00 


• T1004 software (included free with 


• HOOQ PC board only— $35.00 


T1004 order)— $10.00 


• 11000, assembled and tested— 


Add $5.00 S&H to any order. Check or 


$77.00 


money order only. 



List. (Software can also be pur- 
chased from that same supplier 
if you're not buying anything 
else from them and you have no 



way of downloading it from the 
RE-BBS.) With the T1004, you 
are on your way to automatic 
troubleshooting. R-E 



Earn Your B.S. Degree 

in 

ELECTRONICS 

or 
COMPUTERS 




By Studying at Home 

Grantham College of Engineerir 
now in our 42nd year, is highly e 
perienced in "distance education" 
teaching by correspondence — throu 
printed materials, computer materia 
fax, and phone. 

No commuting to class. Study 
your own pace, while continuing 
your present job. Learn from easy-t 
understand but complete and thorou 
lesson materials, with additional hi 
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Our Computer B.S, Degree Pi 
gram includes courses in BASI 
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Assembly Language, MS DOS, CAD 
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Our Electronics B.S. Degree P: 
gram includes courses in Solid-St 
Circuit Analysis and Design, Cont 
Systems, Analog/ Digital Communi 
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An important part of being p 
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college degree, and the absolutely ne< 
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Grantham can help you both way 
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Write or phone for our i 
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see mailing address below. 



Accredited by 

the Accrediting Commission of the 

National Home Study Council 



GRANTHAM 

College of Engineer in t 

Grantham College Road 
Slidell, LA 70460 



HANDI TALKIE 



continued from page 42 






1 



1 
z 

2 



60 



bushing to provide a gap be- 
tween the top of the microphone 
and the holes in the face of the 
bushing, (that permits sound to 
enter unimpeded.) 

It is recommended that the 
bushing be snapped into the ex- 
trusion before performing the 
microphone bonding step or the 
plastic snaps will interfere with 
the microphone. 

Refer to the mechanical 
layout drawing Fig. 6 as a guide 
for mechanical assembly. At- 
tach the front panel to the PC 
board. First attach hex ring 
nuts to the front of both 
squelch potentiometer R25 
and volume potentiometer R26, 
and coaxial BNC connector Jl. 
Be sure that the PC board abuts 
the front panel and is fastened 
with hex ring nuts on the out- 
side of the threaded barrels of 
the potentiometers and BNC 
connector. Avoid placing exces- 
sive torque on the potentiome- 
ters by holding the hex ring 
nuts behind the panel with 
pliers or wrench while tighten- 
ing thejront nuts with another 
wrench. 

7b complete the assembly of 
the transceiver, place the speak- 
er and grill inside the alumi- 
num housing extrusion and 
fasten it with four No. 6-32 x 
5/16-inch Philips-head screws, 
internal tooth lock washers, 
and nuts. Connect all cables to 
their proper jacks on the PC 
board, and slide the assembly 
into the housing. Depress the 
transmit switch SI shaft so that 
it slides into the housing. (The 
transmit switch button cannot 
be attached until the board is 
inserted In the extrusion.) 

Attach the end panels with 
No, 440 self-tapping screws. 
Slide the knobs on the 0.125- 
inch diameter squelch and vol- 
ume potentiometer shafts (R25 
and R26) and lock them in posi- 
tion with a 0.050-inch Allen 
wrench. 

Calibration & troubleshooting 

Charge the power cells by con- 
necting them to the wall outlet- 




FIG. 7— COMPLETED E-Comm CIRCUIT BOARD shown actual size. Note vertica 
mounted axial-leaded components R1, L4, L5, L7, L8 and 04. 



mounted AC to 12-volt DC 
adapter for 24 hours. Be sure 
the power switch is off while 
the power pack is being 
charged. The following test 
equipment is required to cali- 
brate the E-Comm transceiver: 

• Oscilloscope (one that is 50 
MHz or faster) 

• Frequency counter 

• Digital multimeter 

• Plastic coil-tuning sticks 

• A 50 -ohm dummy load 

An FM-modulated RF source 
is helpful but Is not a require- 
ment for calibrating the trans- 
ceiver. The 50-ohm dummy can 
be made by wiring ten 4 70- ohm 
resistors in parallel with short 
leads. Be sure that inductor L8 
is not installed before starting 
the procedure! 

First tune the transmitter. 
Note: while adjusting the trans- 
mitter avoid touching any of the 
output circuit components be- 
cause some high voltages are 
developed there. Turn on the 
power switch and connect the 
oscilloscope leads to pin 1 of 
IC2, the quad-NAND Schmitt 
trigger and observe the wave- 
forms while pressing the trans- 
mit switch. Tweak Inductors LI 
and then L2 until a clean sin- 
usoidal waveform is observed. 
(The frequency should be about 
27.145 MHz.) 

Disconnect the oscilloscope 
and attach a frequency counter 
to pin 1 of IC2 through the high 
impedance input of the counter. 



and adjust inductor L9 to si 
the frequency to 27.145 MH: 
Reconnect the scope again an 
fine tune inductors LI and L2 i 
get the best looking waveforn 
The waveform amplitud 
should be between 3 and 6 voli 
peak-to-peak. If the waveform 
satisfactory, solder inductor L 
into the circuit board and a 
tach the 50-ohm dummy load I 
the BNC antenna jack. 

Attach a current meter in si 
ries with the power pack or th 
DC supply to adjust the final R 
amplifier. Hook up the outpi 
pin of Jl to the oscilloscope an 
set it to 10 volts per divisioi 
While observing the currer 
meter, press the transmi 
switch and look at the wav< 
form. Quickly tweak capacitc 
C30 so that the current is les 
than 400 milliamperes and th 
output voltage across th 
dummy load is about 35 volt 
peak-fo-peak. 

To obtain maximum efficier 
cy, fine tune inductors LI an 
L2 and capacitor C30 to set th 
output power as close as poss 
ble to the optimum value. Ths 
value is expressed as (V out pea 
x 0.707) 2 /50 divided by the ir 
put power (V jn DC X I in DC 
(This is a "trial and error"' ste 
that calls for patience.) Do nc 
try to set the output to ma? 
imum power! 

If the 400-milliampere ma> 

imum input current is exceec 

continued on page 9 








differenti*probe is an oscillttKXSpe at 
cessorytijt permits you*o rake me 

ts from two points in a circQit 
if reference to ground. That enables the 
oscilloscope to be safely grounded without the 
need for op to isolators or isolation transfor- 
mers. The probe can also make accurate mea- 
surements of small signal differences even in 
the presence of very high common-mode volt- 
age gtM 

The probe, in effect, moves the input termi- 
nals from the front panel of the scope to the end 
of the probe. The inputs of a differential probe 
with appropriate input ratings can, for exam- 
ple, measure power semicondutor circuits be- 
cause no reference to ground is needed. Both 
positive and negative sides of the balanced in- 
put offer high impedance to ground. High-im- 
pedance differential probes increase the input 
Bistance and reduce the effective input capae- 
ice of the oscilloscope. 




The low-cost diflerential probe shown in Fig. 
1 was designed primarily for industrial elec- 
tronic maintenance applications where AC volt- 
ages up to 500 volts rms are present. Table 1 
gives the leading specifications of that instru- 
ment. It has selectable attenuation ratios of 
20:1 and 200:1, 

Figure 3 is a simplified schematic of the dif- 
ferential probe showing how it is connected 
between the circuit under test and the scope. A 
built-in differential amplifier converts the high- 
voltage differential input signal to a low-volt- 
age, single-ended output for a general purpose 
oscilloscope. 

Electronic test labs that perform a wide vari- 
ety of measurements are likely to own one or 
more differential probes. But until recently dif- 
ferential probes have been quite expensive 
(more than $2000}. As a result, you might still 
see oscilloscopes "floated" above ground while 
tests of ungrounded circuits are made. Wh tie it 
is never recommended, it can be done safely 
only if low voltages, say 1 to 28 volts, are in- 
volved—and proper safety precautions art- 
taken. Some use a battery-powered portable 
scope, others remove the ground pin from the 
scope's AC line plug or rmffouierwaysio 
ground'* the scope's chassis. 

However, if one is to measure hundreds 
volts in ungrounded circuits, the case of 
oscilloscope and any metal parts touching that 
case are at a lethal potential. The scope operator 
could be electrocuted! That is why demand is 
increasing for low-cost, industrial-strength dif- 
ferential probes that can make accurate mea- 
surements safely on the JafitoHfrfQor with, 
conventional grou nde&f^ejgJL 
cilloscope. ^^B 



i ine 

"un- 

ls\ 
FthJ 



Learn how to use the active differential probe to make 
measurements m ungrounded systems — safety 



'Walter Dorfman is a Senior Electrical 



at Avex Probes, Inc. 





v 

,1 | J ' y 



FIG. T— API MODEL SI-900 ACTIVE DIF- 
FERENTIAL PROBE suitable lor making 
measurements to ± 1000 volts DC. 

High-voltage application 

The best way to explain the 
value of a differential probe in 
an industrial setting is to review 
a problem that occurred in an 
ungrounded closed-loop control 
system and that was solved in a 
safe and timely manner with 
the probe. 

A conveyer belt in a manufac- 
turing plant was exhibiting 
radical speed fluctuations; it 
would alternately slow almost to 
a halt and then speed up to a 
rate that endangered nearby 
personnel. Solving this control 
problem was important be- 
cause, unless it was corrected 
promptly, the production line 
would be shut down. 

Figure 3 is the schematic for 
the belt drive in a control system 
closed around a programmable 
logic controller (PLC). The belt- 
drive DC motor is driven by a 
single-phase, full-wave SCR 
bridge that is electrically iso- 
gj lated from the PLC by four iso- 
S Iating SCR gate trigger mod- 
fe ules. The motor is electrically 
a isolated from a tachometer that 
cj sends velocity signals back to 
s' the PLC, and both bridge and 
z motor are electrically isolated 
8 from the 220-volt AC line by a 
| 1:1 power isolation transformer, 
g When the belt was running, 

w persons close to it could hear 
the sound of the drive motor 
62 change pitch as they observed 



the erratic belt speed. In at- 
tempting to trace the cause of 
the problem, the first step was 
to connect a conventional dig- 
ital multimeter across the 
motor's armature terminals to 
verify that the belt speed 
changes corresponded with 
motor voltage changes. Then 
the conveyor belt was discon- 
nected from the drive motor 
sheave to verify that the the 
motor's speed variations were 
not due to variations in belt 
loading. 

Troubleshooting plan 

A troubleshooting plan was 
formulated to rule out possible 
faults and isolate the cause to 
one or more of the system ele- 
ments. Figure 3 shows that the 
PLC is referenced to Earth 
ground. But the rest of the cir- 
cuit is isolated from ground to 
prevent a build-up of damaging 
or hazardous potentials, due to 
an insulation failure, within the 
motor-driven conveyor-belt sys- 
tem. An oscilloscope referenced 
and connected to Earth ground 
cannot make accurate measure- 
ments in a circuit that is not 
referenced to the same ground. 

The maximum peak-to-peak 
voltage that could appear in the 
bridge is about 622 volts, based 
on the characteristics of a sine 
wave for 220-volt AC. (The rms 
voltage must be multiplied by a 



¥ 



DC TO DC 
CONVERTER 






TO THE 

CIRCUIT 

UNDER 

TEST 



RED 



BLACK 





factor of 2.83 to obtain t 
peak-to-peak voltage.) Exa 
ination of the control diagr; 
showed that differential mi 
surement techniques we 
needed to make accurate a 
safe measurements of tr 
"floating" system. 

It would be necessary to cht 
logic-level SCR gate sign; 
riding on the 220-volt AC lii 
Any differential probe suita 
for making those measu 
ments had to be capable of a 
celling the large peak-to-pe 
AC waveform, leaving only t 
desired logic-level signals, ei 
mated at 3 and 12 volts DC, 
analysis. 

The differential probe v» 
first connected to Earth grou 
with the oscilloscope (BNC) ct 
nector. Then the probe was cc 
nected to the oscilloscope, 
this case, the internal pov 
supply was used so the pre 
could then be turned "on. 

Knowing that voltages in < 
cess of 622 volts AC peak- 
peak would be present, a pre 
attenuation range of 200:1 v* 
selected. (Table 1 shows that 
the probe used, the maxiim 
working voltage to ground a 
between inputs is 500 vo 
rms, and the maximum non-< 
structive input is 700 volts , 
rms or 1000 volts DC.) 

The 622 volts is divided 
200 to become a 3.11-volt s 



-^-v 



ATTENUATION 
NETWORK 

FIG. 2— A SCHEMATIC OF AN ACTIVE DIFFERENTIAL PROBE that can be Interns 
powered by tour 1.5-volt cells or an AC to DC converter. 




TABLE 1- 


-LEADING SPECS OF API PROBE 


Band width 


DC to 15 MHz 


Accuracy 


±2% (nominal) 


Attenuation ratio 


20:1 and 200:1 (selectable) 


Input resistance 


2 Megohms 


input capacitance 


25 pF (each side grounded) 


Input range 


±700 V DC + peak AC 

(200:1 attenuation) 
± 70 V DC + peak AC 

(200:1 or 20:1 attentuation) 


Max. common 
mode input 


500 V rms 


Common mode 
rejection ratio 


70 dB {§ 1 kHz 


Max. output 


±3.5 V into 1 Megohm 


Output offset 


±5mV{10°Cto40°C) 


Power requirements 


Four 1 .5 V AA cells or 
6 V DC, 50 m A adapter 













PROGRAMMABLE 

LOGIC 

CONTROLLER 



■=■ /77T7 



ISOLATING 

SCR GATE 

TRIGGER MODULES 



SCR1 



SCR2 



ISOLATION 

TRANSFORMER 

I 1 



to 



220V 
AC i 
LINE 



SCR3 



& 



O 



~& 



SCR4 




KD 1 



ISOLATED 
TACHOMETER 



I 






FIG. 3— A CONVEYOR BELT SPEED CONTROL system, isolated from Earth ground, 
includes a programmable logic controller (PLC), a full-wave, single-phase SCR bridge, 
DC motor with isolated tachometer, and four isolating SCR gate-triggering modules. 



nal, (The displayed output volt- 
age had to be kept within the 
±3.5 volts limit of the probe.) 

The two probe input leads 
were then carefully connected 
across the 220-volt AC line feed- 
ing the 1:1 isolation trans- 
former. The oscilloscope dis- 
played the 3. 11 -volts peak-to- 
peak sine wave shown in Fig. 4- 
a. The regularity of the scaled- 
down sine wave showed that 
there were no faults in the line 
voltage. 

Both probes were moved to 
the secondary of the isolation 



transformer and a waveform es- 
sentially the same as the 622- 
volt peak-to-peak sine wave- 
form of Fig. 4-a appeared; it is 
shown as Fig. 4-b. However, 
small distortions and ampli- 
tude changes were seen on the 
negative peaks, and they were 
in synch with motor-speed vari- 
ations. The electrical noise in 
the waveform was believed to be 
due to the reflected loading 
effects of the motor's power and 
speed changes. 

The differential probe leads 
were than connected across the 



motor's armature, and the 
periodic high-frequency oscilla- 
tions shown in Fig. 4-c were 
seen. Their occurance matched 
the motor's speed variations. 
Next the probe was connected 
across the anode ( + ) and cath- 
ode ( - ) terminals of each of the 
four SCR's in the bridge, and 
their waveforms were observed. 

As shown in Fig. 5, all the 
SCR's exhibited some waveform 
distortion, but one of them, Fig. 
5-c exhibited more severe dis- 
tortion than the others. 

As the next step, the probe 
was connected across the gate 
( + ) to cathode ( - ) terminals of 
each of the three SCR's that 
showed lower anode-to-cathode 
noise voltages. The differentia] 
probe successfully cancelled the 
622 volts peak-to-peak AC on 
which the gate-to-cathode volt- 
ages were riding. The result was 
clean, normal gate trigger wave- 
forms with nominal 3-volt 
peaks, as shown in Figs. 6-a, 6- 
b, and 6-d. 

However, the remaining 
SCR's gate-to-cathode voltage 
waveform, Fig. 6-c, showed 
time-varying gate-trigger 
pulses. (It was the same SCR 
that had shown the highest 
anode-to-cathode jitter in Fig. 
5-c) Some pulses in Fig. 6-c 
started earlier and others start- 




RG. 4— VOLTAGE WAVEFORMS viewer 
at 220-volt AC input: transformer prl 
mary a, transformer secondary b, ant 
motor armature (load) c. 



Si 

01 



is 





3 



64 



FIG. 5— ANODE-TO-CATHODE VOLT- 
AGES viewed at each bridge SCR (trig- 
gered at 90° into a positive peak supply 
voltage): SCR1 a, SCR2 b, SCR3 c, and 
SCR4 d. 

ed later than the nominal times 
seen for the other three gate-to- 
cathode waveforms. 

Identifying the culprit 

A pattern had now been es- 
tablished linking the trouble to 
one SCR channel. It was next 
decided to determine the quali- 
ty of the output signals from the 
PLC. To observe the PLC output 
lines, which are referenced to 
system/Earth ground, the black 
( - ) lead of the differential probe 
was connected to system 
ground. Because 12-volt logic 



signals were to be viewed, the 
differential probes attenuator 
was switched to 20:1 (12 volts/ 
20 = 0.6 volt), and the os- 
cilloscope's vertical sensitivity 
of 0. 1 volt/division was selected. 

Three of the four 12-volt logic 
signals from the PLC to the SCR 
gate-trigger lines appeared nor- 
mal, as shown in Fig. 6-e, 6-f, 
and 6-h. However, the Fig. 6-g 
waveform was distorted by low- 
level reflected noise that tracked 
with the motor's speed varia- 
tions. It was the same SCR 
channel that had shown gate- 
to-cathode electrical noise in 
Fig. 5-c. 

That finding narrowed the 
cause of the problem down to 
one SCR channel and it was 
thought to be either a faulty 
PLC-to-SCR gate isolating trig- 
ger module or a malfunctioning 
SCR. A new plug-in module was 
then substituted for the one 
that appeared to be faulty, and 
the problem was quickly solved. 

The differential probe dis- 
cussed in this article is sold in 
the United States by three dif- 
ferent suppliers: Avex Probes 
Inc. (API) as the SI-9000; Test 
Probes, Inc.(TPl) as the ADF15, 



PROBE SUPPLIERS 



3V 



3V 



3V 



3V 



+ 12V 

0- 
+ 12V 

0- 
+ 12V 

0- 
+ 12V 



REaECTFD 
NOISE 



I 



JNUA 



FIG, 6— GATE-TO-CATHODE VOLTAGES 
viewed at the input of gate terminals of 
SCR1 to SCR4 a, b, c, and of, and output 
signals from the PLC a, b, c, and d. 



Avex Probes Inc. (API) 
PO Box 1026 
Bensalem, PA 19020 
215-638-3300 

CIRCLE 316 ON FREE INFORMATION CA 

Hewlett-Packard 

PO Box 612350 

San Jose, CA 95161-2350 

800-452-4848 

CIRCLE 317 ON FREE INFORMATION CA 

ITT Pomona 

1500 East Ninth St. 
Pomona, CA 91769 
714-469-2900 

CIRCLE 318 ON FREE INFORMATION CAI 

Jensen Tools, Inc. 

7815 South 46th St. 
Phoenix, AZ 85044-5399 
602-968-6231 

CIRCLE 313 ON FREE INFORMATION CAI 

Probe Master Inc. 
4898 Ronson Court 
San Diego. CA 92111 
800-772-1519 

CIRCLE 320 ON FREE INFORMATION CAI 

Tektronix 

POBoxSG 

Beaverton, OR 97077 
503-627-7111 

CIRCLE 321 ON FREE INFORMATION CAF 

Test Probes, Inc. (TPI) 

9178 Brown Deer Road 
San Diego, CA 921 21 
(616) 552-2090 

CIRCLE 322 ON FREE INFORMATION CAF 



and Probe Master as t v 
PM4230. 

For purposes of compariso 
consider two other differenti 
probes, the Tektronix P604 
and the Hewlett-Packard Y 
1141A/1142A. The Tektron 
system consists of three sep 
rate cable-connected units: 
probe head, an amplifier, and* 
AC-line operated power supp 
It has a common-mode rejectic 
ratio (CMRR) of 10,000:1, an i; 
put resistance of 1 megohr 
and an input capacitance of i 
picofarads. Its maximum ban 
width is 100 MHz, and its ma 
imum DC plus peak AC is ± 2E 
volts. 

The HP 1141A differenti 
probe is a 1 x FET differenti 
probe with a 200-MHz bam 
width and a CMRR of 3000: 
The probe has an input resi 
tance of 1 megohm and an inpi 
capacitance of 7 picofarads, 
must be used wi th the HP 1 145 
probe control and power mo' 
ule system. R 



FROM 

NotWorking 

Networking 






Bring your knowledge to bear 
on several tough LAN case histories. 



PARTS 1 AND 2 OF THIS THREE-EART 

series on troubleshooting LANs 
presented technical back- 
ground on network tech- 
nologies (in Part 1), and on tools 
and test equipment (in Part 2). 
This time we put our knowledge 
to work in diagnosing and solv- 
ing network problems of vary- 
ing difficulty. 

In each case, we will describe 
the type of LAN, symptoms 
manifested, fault isolation tech- 
niques, use of test equipment, 
and repair methods. Tb follow 
the discussion, it is important 
to have at least a basic under- 
standing of LAN technologies 
and test equipment as de- 
scribed in parts 1 and 2. So if 
you are unsure about anything 
discussed so far, reread those 
parts before continuing. 



The computer ate my work! 

This one happened at a local 
metal fabrication shop; the 
symptoms drove the company's 
finance people up the wall! That 
shop had five XT clones commu- 
nicating with an IBM PC-AT file 
server via Ethernet. For a long 
time, the network had been re- 
liable, but after several years of 
use, it began to run slower and 
slower whenever users ran 
order entry and accounting pro- 
grams off the file server. Error 
messages began to appear, and 
sometimes users had to repeat 
the process. Troubleshooting 
began when several people in 
the order entry department 



GARY McCLELLAN 

complained of trashed data. 

Several users were affected, 
so it seemed unlikely that their 
computers were at fault. That 
left the Ethernet backbone ca- 
ble and the file server as sus- 
pects. The backbone cable 
could have been the problem, 
but it didn't seem likely. Then 
someone discovered that a sel- 
dom-used word-processing pro- 
gram ran fine, so we ruled out 
the possibility of cable fault. 
That left the file server and hard 
disk as a possible culprit. 

That evening we shut down 
the network and ran a "disk 
doctor" program on the file serv- 
er. Those programs are available 
from several sources, including 
Symantec (Norton Utilities), 
Central Point Software (PC 
Tools), and Gibson Research 
(SpinRite). What these pro- 
grams do is perform a non-de- 
structive low-level format of a 
disk drive. Typically, such pro- 
grams work by reading a track 
of data from the drive, format- 
ting that track, and rewriting 
the data. Any bad sectors de- 
tected along the way get mapped 
out, and the data gets moved 
elsewhere, if possible. Figure 1 
shows a sample screen from the 
Calibrate utility included with 
versions 6.x of the Norton Util- 
ities. 

A related function often goes 
by the name of disk defragmen f- 
ing, which attempts to group 
logically related segments of a 
file together physically in con- 




secutive sectors of a disk. Doing 
so can dramatically increase the 
speed with which DOS reads 
files. A disk becomes frag- 
mented because, when a file is 
erased, DOS subsequently adds 
the now-unused sectors to a 
pool of sectors that might sub- 
sequently be reused. A par- 
ticular group of erased sectors 
might not contain enough 
space to hold an entire file, so 
DOS puts parts of the file in 
non-adjacent areas across the 
disk. The result is that when 
loading the program or data file, 
DOS sends the read/write head 
all over the surface of the disk, 
rather than lapping up sectors 
one by one. That jerky head mo- 
tion can really slow things 
down. It is not unusual for over- 
all operation to be speeded up bv 
10-20% or even more simply bj 
"doctoring" the hard disk. Nor 
ton and Central Point both in- 
clude disk defraggers as well. 

Anyway, running a disk doc 
tor program on the fabricator 
shop's server solved the prob 
lem. To avoid that type of prob 
Iem, run a disk doctor progran 
a minimum of every six month: 
to catch bad cylinders and pre 
vent data loss. If you encounte 
many bad cylinders, say 5% o 
more, you should replace tha 
hard disk before a catastrophi 
failure occurs! 

The dead PC 

Many LAN problems go lik 
this: A user cannot log onto tb 



H-Help 



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it ut 11 pcrforn 4 naln ti MM I 

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FIG. 1— SOMETIMES NETWORK FAULTS aren't network faults at all, but faults with 
hard-disk drives. In an MS-DOS environment, Norton's Calibrate utility can help to 
locate and lock out bad sectors. 



network, or a PC suddenly 
drops offline — but other users 
remain unaffected. Following 
are two examples of this type of 
problem, along with corre- 
sponding solutions. 

Example one occurred in a 
parts distributor's office. The 
LAN consisted of five clone PC's 
and a generic 80286 file server 
tied together via ARCnet. 
ARCnet operates over RG-58 
thin coaxial cable that runs 
from computer to computer. 

First, we tested the sick PC 
off-line and found it to be func- 
tional. That left the Network In- 
terface Card (NIC) and LAN 
cabling as suspects. First we in- 
spected the coax cables and they 
looked good. But a gentle tug on 
a loose BNC cable connector 
caused it to come off. Replacing 
the connector brought the com- 
puter back to life. 
Generally speaking, con- 
gj nector faults are a major prob- 
S! Jem on LAN's. Most BNC 
fe connectors are crimp-on types, 
§ and if Installed improperly, 
<S eventually they fail — but not be- 
| fore becoming intermittent and 
z causing lots of grief! Connector 
8 problems usually develop sev- 
g eral years after their initial in- 
|f stallation; often they're caused 
iu by oxidation of contacts. For 
problem installations, we prefer 
66 soldered to crimp-on BNC con- 



nectors. They take 5 to 10 min- 
utes longer to install, but are far 
more reliable. 

Many connector problems are 
caused by users who acciden- 
tally damage cables by crushing 
them under chair legs, or drop- 
ping equipment on them. Our 
troubleshooting kit includes a 
collection of 10-foot cables 
which have coaxial BNC con- 
nectors, triple twisted-pair 
RJ-11 connectors, and quad 
twisted-pair RJ-45 connectors. 
The cables are for on-site sub- 
stitution of questionable ca- 
bles. 

Example two in this category 
concerned a dead computer in a 
medical billing office. The com- 
pany used five IBM PC's linked 
by telephone-type unshielded 
twisted pair (UTP) cabling into a 
Compaq 386 configured as a 
hub. The hub serves as both a 
file server and as a central point 
to which all cabling returns. 

We tested the problem PC, 
and it appeared to be working. It 
just wouldn't log onto the net- 
work. We substituted a different 
drop cable between computer 
and wall outlet; the new cable 
worked for a while and then 
quit. Next we substituted a PC 
from the office of a vacationing 
user, but without success. 

At that point the problem 
could have been anywhere, in- 



cluding the computer, its NIC 
the cable plugged into the wa 
outlet, or even the wiring bac 
to the hub. 

First, we checked the old wa 
cable with the Paladi 
PatchCheck tester (discussed i 
the last article). Patch Chec 
checks cables in seconds, if yo 
can access the modular plug 
on both ends. Pin 2 showed 
dim indication on the teste 
suggesting high resistance. TA 
didn't know which end was bac 
so we replaced the connectors i 
both ends. The cable then tes 
ed good, so we reinstalled it an 
were able to log onto the ne 
work briefly. But then troub] 
developed again. On a nunc! 
we pushed and held the modi 
lar connector in the wall outle 
The user could log onto the ne 
work and work normally— unt 
we let go of the connector. The 
the PC crashed. Replacing th 
wall outlet solved the problen 

In general, most twisted-pai 
cable problems are caused b 
bad crimps or by users pullln 
individual strands out of th 
connectors. In the present cas< 
the initial installer used chea 
connectors that probably wer 
not crimped fully, which in tur 
caused resistance to increas 
over time. As for the wall outle 
close inspection showed th£ 
the pins were partly covered by 
greenish film, probably cause 
by moisture in the wall corroc 
ing the faulty gold plating on th 
pins. 

If you want to avoid a career i 
connector replacement yo 
should always use quality cabl 
and wall-socket connectors. 

Warehouse madness 

The problems described so fa 
represent roughly 80% of th 
faults you will encounter o 
computer LAN's. But there ar 
other kinds of problems thi 
will tax your troubleshootin 
abilities, and that also requii 
specialized test equipment. Ou 
next case is a good example. 

A firm relocated to a ne^ 
headquarters 100 miles awa; 
leaving behind a warehouse 
The new system used an IBI 
midrange computer (at heat 
quarters) and CRT terminal 
and printers (in the wart 



house), all connected via mod- 
ems and a dedicated telephone 
line. The purpose of this ar- 
rangement was to generate cus- 
tomer shipping orders. One day 
all the terminals and printers in 
the warehouse stopped cold. 
The data processing manager 
(DPM) of the company found 
that his equipment was not 
working properly, and he 
blamed the telephone line. The 
locai telephone company check- 
ed its line and pronounced it 
good! So where was the prob- 
lem? 

One possibility was that the 
fault was somewhere in the 
warehouse, between the 
modem and the outside line 
connections. With permission, 
we inspected the modem wiring 
in the telephone cable closet. It 
looked good, but then we mea- 
sured the line voltage with a 
DMM. It read zero! We had ex- 
pected 2 to 10 millivolts of AC 
noise, typical on a terminated 
line. A quick resistance check 
showed 7 ohms. There was a 
short in the wiring! 

We then spent several hours 
walking between modem and 
cable closet, disconnecting wir- 
ing, and eliminating various 
suspects. One look at the huge 
bundles of wiring on the wall of 
the building was enough to dis- 
courage fault finding by visual 
inspection! 

The solution was to use a time 
domain reflectometer {TDR), 
which can locate faults along 
the cable. After making sure the 
outside telephone line and 
modem cable were still discon- 
nected, we attached a MicroTest 
Cable Scanner handheld TDR 
to the line in the closet. The 
TDR indicated some irreg- 
ularity about 70 feet away. 
which put the fault near the 
modem. Then we made another 
measurement near the modem 
end, and the cable scanner indi- 
cated a dead short. 

Then we traced the wiring 
into a storage closet where the 
red and white twisted-pair cable 
ran through a hole in a steel 
riser and up the wall. Close in- 
spection of the wires running 
through the hole revealed that a 
sharp edge had cut through the 
insulation and shorted the ca- 



ble. Insulating the wires with 
electrical tape brought the net- 
work back on-line. 
The problem of different or- 



NETWORK BACKGROUND 

The following are reference materi- 
als, equipment suppliers, and network- 
related standards organizations. 
References: 

• The Practical Guide to Local Area 
Networks, Rowland Archer, Osborne- 
McGraw Hill. Good introduction to cable 
types, topologies, and access methods. 

• Networking IBM PC's, Michael Durr, 
Que Corporation. Chapter 14 contains 
good overview of bridges, routers, and 
gateways. 

• LAN Magazine, 600 Harrison Street, 
San Francisco, CA 94107 (415) 
905-2200. 

Suppliers: 

• Black Box Corporation, P.O. Box 
12800, Pittsburgh, PA 15241, (412) 
746-5530. 

• Cable Express Corporation, 500 East 
Brighton Avenue, Syracuse, NY 13210, 
(3151 476-3100. 

• Contact East, 335 Willo Street South, 
North Andover, MD 01845, (508) 
688-7829 

• JDR Microdeviees, 2233 Samaritan 
Drive, San Jose, CA 95124, (800) 
538-5000. 

• Jensen Tools, inc., 7815 S, 46th 
Street. Phoenix, AZ 85044, (602) 
968-6231. 

Standards Organizations: 

• American National Standards In- 
stitute, 1430 Broadway, New York, NY 
10018, (212). 642-4900. 

• IEEE Headquarters, 345 E. 47th 
Street, New York. NY 10017-2394, (212) 
705-7900. 



RESOURCES 

The following are addresses of man- 
ufacturers whose products were dis- 
cussed in this series of articles. Contact 
those companies for current pricing and 
more information, 

• Paladin Corporation, 3543 Old Cone- 
jo Rd., Newbury Park, CA 92123. (800) 
272-8665. 

• MicroTest, Inc., 3519 E. Shea Blvd. 
Suite 134, Phoenix, A2 85028, (BOO) 
526-9675. 

• Radio Amateur's Handbook, 
American Radio Relay League, New- 
ington, CT 06111. 

• Tektronix, Inc., Redmond Division, 
625 S. £. Salmon Dr., Redmond, OR 
97756, (800) 833-9200. 

• AMP, Inc., P.O. Box 3606, Harrisburg, 
PA 17105, (717) 561-6168. 

• Gibson Research. 22991 La Cadena 
Dr., Laguna Hills, CA 92653, (714) 
830-2200 

• Symantec Corp., Norton Utilities. 
10201 Torre Ave., Cupertino, CA 
95014-2132. (408) 253-9600. 



ganizations blaming each other 
for faults neither can trace is 
common, because most LAN's 
consist of different products 
from different vendors, includ- 
ing computers, terminals, 
printers, modems, NIC's, ca- 
bles, and more. The solution is 
to learn about your LAN equip- 
ment and service it yourself, or 
find a trustworthy service firm 
that can do it for you. 

Cloak and dagger 

We saved the most fascinating 
LAN servicing case for last. After 
this case was resolved, someone 
must have answered some in- 
teresting questions about his 
late-night activities. 

Here's what happened: A soft- 
ware development firm became 
highly distressed when several 
of its workstations performed 
intermittendy in the middle of a 
rush project. The firm promptiy 
called its regular service compa- 
ny, which in turn concluded 
that there was a bad cable con- 
necting those machines and the 
rest of the LAN. The service 
company recommended tearing 
the old cable out of the wail and 
replacing it. After considering 
the cost of a new cable installa- 
tion, the firm asked that it be 
repaired instead. 

At this point we were called in 
to provide a second opinion. 
Wisely, the service company had 
bypassed the bad cable with a 
temporary one; thus we could 
test the bad cable without shut- 
ting down the LAN. This net- 
work used a series of high-end 
workstations tied together via 
an ARCnet system into a mini- 
computer. A 60- to 100-foot 
length of coaxial cable con- 
nected the LAN with the last twc 
workstations in the chain. Wt 
knew that the cable betweer 
them and the LAN was at fault 

We started troubleshooting b} 
making continuity checks or 
the wiring. Instead of an oper 
circuit, our DMM showed 1( 
ohms between the shell am 
center conductor of one of tru 
BNC connectors extending fron 
the wall. 

There was definitely a short ii 
the cable. But where was it lc 
cated? Our initial response wa 
to confirm the service comp£ 




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FIG. 2— A GOOD ETHERNET CABLE appears like this on a time domain reflectometer 
(TDR), which shows impedance vs. distance. The vertical line in a marks the end ol the 
cable. In b, the vertical line represents a bad cable tap. The TDR can "zoom" into the 
display, and c shows an expanded view of the bad tap. 



ny's assessment, and to recom- 
mend tearing out the old cable. 
However, we first decided to do 
some troubleshooting. 

We rented a Tektronix model 
1502C analog TDR from a local 
instrument rental company. 
(Rental is recommended any- 
time you need an expensive 
piece of equipment for just a few 



days.) We chose this premiere 
TDR because it displays minor 
faults that digital TDR's often 
miss. In the past we have lo- 
cated rusty connectors, loose 
connectors, and watersoaked 
cable sections with the 1502C, 
all of which were missed by a 
digital TDR. The down side of 
an analog TDR is that it re- 



quires more skill to use. 

The 1502C displays distai 
vs. impedance on an L' 
screen. The display sho\ 
along the entire length of 
cable, a continuous "snapsh 
of impedance, which in our c, 
was supposed to be about 
ohms. Shorts cause the trace 
drop to ohms, and op* 
cause the trace to rise off 
display. In operation, you 1( 
for suspect drops and ris 
read the distance directiy off i 
display, and start troubleshc 
ing at the specified locati< 
Figure 2 shows several exa 
pies of TDR displays. 

After connecting the TDR 
the cable, we checked the c 
play, which showed the i 
pected 50-ohms, but witr 
sharp drop about 29 feet awa; 
company manager, who h 
been looking over o 
shoulders, suggested that 
check the ceiling. We lifted o 
ing panels and located the 
ble. Since we had no idea 
distance in the ceiling space, 
guessed at the location and 
spected cable for some distar 
each way from our access poi. 
Above a service closet we fou 
the culprit. Someone had slit 
the cable open and crudt 
spliced another cable to it. 

Upon closer inspection, " 
noticed that the added cal 
was pulled taut, causi; 
strands from the uninsulai 
connections to touch. That, 
turn, reduced signal levels 
the workstations, causing int 
mittent problems. With exci 
ment, we traced the secoi 
cable into a closet where ' 
found a computer and a prin 
hidden behind a row of shelv< 

We showed our findings to t 
manager. He said he wou 
watch the closet and determi 
the identity of the eavesdropp 
A week later he called the serv] 
company and had them rerac 
the splice and replace it with 
crimp-on BNC connector anc 
barrel adapter. Later we hea 
that the computer had been i 
moved from the closet, but t 
manager would not say whetb 
he had caught the guilty pi 
son. If it hadn't been for t 
short, we might never have d 
covered that illegal tap! f 



THIS ARTICLE LOOKS AT THE VER- 

satile 555 monolllhic integrated 
timing circuit as an astable 
multivibrator, the tlip-side of its 
capabilities as a monostable 
multivibrator in time-delay cir- 
cuits. A recent article (Sep- 
tember R-E, pg. 58} explored the 
role of the 555 in the monosta- 
ble mode. 

Now you'll find out how to 
build many different kinds of 
circuits with the 555 configured 
as a self-triggering oscillator. 
You will want to build the cir- 
cuits that can generate a variety 
of square or rectangular wave- 
forms, wail like a police car. imi- 
tate the jarring he-haw sound of 
European emergency vehicles, 
or reproduce the Klaxon alarm 
of the Star Treks' starship Enter- 
prise. 

The last article on the 555 as a 
monostable multivibrator in- 
cluded a functional block di- 
agram and an electrical sche- 
matic of the chip. You might 
want to refer back to those fig- 
ures if you want more detailed 
information about how the 555 
is organized. Figure 1 is a pin- 
out diagram of the 555 as pack- 
aged in the most common 8-pin 
DIP. It was pointed out in the 
last article that, although a ma- 
ture device, the 555 remains 
one of the most popular IC's 
available today. 

At least five major semicon- 
ductor firms in the U.S. and Ja- 
pan make the 555. There is also 
a dual version, the 556, that has 
two identical 555s on a single 
chip. The device is usually pack- 
aged in a 14-pin DIP A quad ver- 
sion, the 558, has four inden- 
tical 555 s on a single chip, and 
it is packaged in a 16-pin DIE 
The alternate source suppliers 
usually include the numerals 
55. 56 or 58 in their own desig- 
nations for those devices. 

The 555 occupies a strange 
position in the universe of inte- 
grated circuits. Classed as a lin- 
ear IC because it can be 
triggered either by linear or dig- 
ital signals, its output is always 
digital — in the form of rec- 
tangular or square waves or 
pulses. 

The 555 in a monostable mul- 
tivibrator circuit (also called a 
timer, time delay, or one-shot) 



THE 555: 

A VERSATILE 

OSCILLATOR 



Learn how to build the 555 IC Into 
oscillator circuits whose frequency you c 
change so they'll wail, warble, and honk. 

RAY M. MARSTON 



generates a fixed-length output 
pulse for each trigger pulse at 
its input. This can be demon- 
strated with the circuit in Fig. 
2. By contrast, the 555 in an 
astable multivibrator circuit is 
shown in Fig. 3. It has no stable 
output states and no external 



GROUND 
TRIGGER 
OUTPUT 
RESET 



T~T 



555 



DISCHARGE 
THRESHOLD 

CONTROL 
VOLTAGE 



FIG. 1— PINOUT DIAGRAM OF THE 555. 

trigger is necessary to start cir- 
cuit oscillation; it is said to be 
self-triggering. This circuit con- 
figuration is also called an 
oscillator, signal generator, 
pulse generator, or a rectangle- 
wave generator. 

As long as power is applied to 
the astable circuit, the output 
continually switches back and 
forth between the high and low 
states at a regular rate or fre- 
quency. The time in the high 
state (pulse width) and the time 
in the low state (space length) 
depend on the selection of exter- 
nal resistors and capacitors. Be- 
cause of its relatively high 
output, the 555 in an astable 
circuit can drive LED's, speak- 
ers, and meters directly. 



Astable operation 

In the monostable multi- 
vibrator circuit in Fig. 2, output 
pin 3, discharge pin 7, and 
threshold pin 6 are held low 
when the circuit is quiescent. A 
monostable timing period can 
be started by driving trigger 
pin 2 low with pushbutton 
switch Si. That causes output 
pin 3 to switch high, while 
discharge pin 7 is released and 
free to follow the voltage across 
CI. Voltage rises exponentially 
through Rl toward the supply 



+ 5VTQ + 15V 



1 

: ;ri 
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II 7 f 


1 o 

8 4 


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< 


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OUTPUT 

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FIG. 2 — MONOSTABLE MULTI 
VIBRATOR TIMING CIRCUIT based oi 
the 555. 

voltage. Eventually the voltagi 
at pin 7 rises to two- thirds o 
the supply voltage, and mono 
stable action ceases with pins 3 



o 

o 
•z. 



o 
"G 



70 



6 and 7 grounded by the inter- 
nal circuitry of the 555. 

Examine the astable circuit 
shown in Fig. 3-a. In this circuit 
trigger pin 2 is shorted to 
threshold pin 6, and timing re- 
sistor R2 is wired between pin 2 
and discharge pin 7. When 
power is applied to the circuit, 
capacitor CI charges exponen- 
tially (as it did in Fig. 1) through 
resistors Rl and R2 until the 
voltage on CI reaches two- 



+ 5VT0 + 15V 



Ri;E 

1K<> 



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f * 



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R2 
75K 



e 



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12 




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ov 


























































































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OUTPUT 
AT PIN 3 

OUTPUT 
ACROSS 
CI 



FIG. 3— A ONE-KILQHERTZ ASTABLE 
MULTIVIBRATOR based on the 555, s, 
and waveforms at output pin 3 and 
across CI are shown in b. 

thirds of the supply voltage. At 
that time, monostable action 
ceases and discharge pin 7 re- 
turns to its low state. Capacitor 
CI then discharges exponen- 
tially into pin 7 through R2 un- 
til the voltage on CI falls to one- 
third of the supply voltage, and 
trigger pin 2 is activated. 

At that time, a new monosta- 
ble timing sequence is started 
and CI recharges to two- thirds 
of the supply voltage through re- 
sistors Rl and R2. The whole 
sequence then repeats itself 
over and over with CI alter- 
nately charging to two-thirds of 
the supply voltage through Rl 
and R2, and then discharging 



to one-third of that voltage 
through R2 only. 

Notice that in Fig. 3-a, the val- 
ue of R2 is very large with re- 
spect to the value of Rl. It turns 
out that the oscillation frequen- 
cy of the circuit is largely deter- 
mined by the values of R2 and 
C2. Figure 3-b shows the nearly 
symmetrical square output 
waveform that appears between 
output pin 3 and ground while a 
nearly linear triangle waveform 
is simultaneously generated 
across CI. 

The graph of Fig. 4 shows the 
relationship between the free- 
running frequency of the cir- 
cuit in Fig. 3-a and the capaci- 
tance values of CI with the 
range of R2 values shown on the 
diagonal lines. In this graph the 
contribution of resistor Rl is 
neglected because it is a frac- 
tion of the R2 value. 



















2 

1 
1" 

M 

.001 














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X 


9 \ 


X 


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R2 
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li—* 



555 



5 

jfcCI 55C2 
.01 .01 





FIG. 6— AN STABLE MULTIVIBRA 
with Independent pulse width and sj 
periods variable from 7 to 750 mien 
conds. 



FIG. 4— THE FREE-RUNNING FRE- 
QUENCY OF OSCILLATOR in Fig. 3 as a 
function of capacitance values for CI 
and the resistance value of R2 (when 
large with respect to Rl). 



+ 5VT0 + 15V 



FIG. 5— THIS SQUARE-WAVE GENER- 
ATOR produces a variable frequency of 
650 Hz to 7.2 kHz. 




FIG. 7— ALTERNATE VERSION OF C 
CILLATOR shown in Fig. 6. 

The values of Rl and R2 c 
be varied from 1 kilohm up 
tens of megohms. Resistor 
can, however, have a signifies 
effect on the total circuit ci 
rent consumption because p 
7 is essentially grounded duri 
half of the oscillation cycle. T 
duty cycle or pulse width-i 
space ratio of the circuit can 
preset at a nonsymmetrical v 
ue, if desired, by the choice of 
and R2 values. 

The high time (pulse widt 
and low time (space length) 
this circuit must be calculat 
separately. The pulse width c 
dilation includes the values I 
the timing capacitor CI ai 
both timing resistors Rl ai 
R2. By contrast, the spa 
length formula includes or 
the values of timing capacit 
CI and resistor R2. 



Refer to Fig. 3-b. Pulse width 
(or time to charge capacitor CI 
is: 

t, = 0.7CUR1 +R2) 
Space length or time to dis- 
charge capacitor CI is: 
t 2 = 0.7 C1R2 
The total cycle time is: 
T = t, +t 2 

The ratio of pulse width to the 
total cycle time is the du ty cycle. 
In a 555-based oscillator, the 
duty cycle is defined by the rela- 
tive values of the two timing re- 
sistors Rl and R2: 
Duty cycle = R2/(R1 +2R2) 
Frequency in hertz (Hz) is the 
reciprocal of total cycle time: 
F = 1H". 

The circuit in Fig, 3-a can be 
modified in many different 
ways. Figure 5, for example, 
shows how it can be made into a 
variable-frequency square-wave 
generator by replacing R2 with 
a fixed resistor and potentiome- 
ter in series. The frequency can 
be varied over a range of about 
650 Hz to 7.2 kHz with the val- 
ues of the resistor and potenti- 
ometer R3 shown. If required, 
the frequency span can be fur- 
ther increased by switch-select- 
ing alternative values of CI. 




FIG. 8— A 1.2 kHz OSCILLATOR with a 
duty cycle variable from 1 to 99%. 



"Width-space control 

The circuit in Fig. 3-a can 
generate a fixed-frequency out- 
put waveform with any desired 
pulse width-to-space length 
ratio by selecting the appropri- 
ate values forRl and R2. In each 
operating cycle, CI alternately 
charges through Rl and R2, 



and discharges only through 
R2. For example, if Rl and R2 
have equal values, the circuit 
will generate a 2:1 width-to- 
space ratio. 

The width-to-space periods 
can be independently controlled 
with either the Figs. 6 or 7. In 
Fig. 6, CI alternately charges 
through Rl, diode Dl, and po- 
tentiometer R3, and it dis- 
charges through potentiometer 
R4, diode D2, and R2. In Fig. 7, 
CI alternately charges through 
Rl, potentiometer R3, and di- 
ode Dl, and it discharges 
through potentiometer R4, di- 
ode D2, and R2. In both Fig. 6 
and 7 circuits, R2 protects the 
555 if potentiometer R4 is 
shorted. 




+ 5VT0 + 1SV 



555 



CI ^ C2i 



1 



OUTPUT 



J A 



FIG. 9— AN ALTERNATE VERSION OF 
OSCILLATOR shown in Fig. 6. 

+ 5VTO + 15V 



>2.2K > 



C3 
tlfcif 



Dl 

IN41M 

— N— 



A2 
1.1K 



R3 

1K 



R4 
75K 



555 



;C1 

.47 



I 



n 



OUTPUT 



IC2 OUTPt 



FIG. 10— A PRECISION LOW-FREQUEN- 
CY OSCILLATOR with a frequency of 
about 20 Hz. 

In the circuits of Figs. 6 and 
7, the width-to-space periods 
can be independently varied 
over about a 100:1 range, en- 



abling the width-to-space ratio 
to be varied from 100:1 to 1:100. 
The oscillation frequency varies 
as the ratio is altered. 

Figures 8 and 9 show alter- 
nate ways of connecting the 555 
in the astable mode so that the 
width-to-space ratio can be var- 
ied without altering the oscillat- 
ing frequency. In those circuits, 
the pulse width period automat- 
ically increases as the space 
length period decreases, and 
vice versa. Therefore, the total 
period of each operating cycle is 
constant. In those circuits, the 
feature of interest is the duty 
cycle. In Figs, 8 and 9, the duty 
cycle can be varied from 1% to 
99% with potentiometer R3. 

In the circuit of Fig. 8, CI al- 
ternately charges through Rl, 
the upper half of R3, and Dl, 
and it discharges through D2, 
R2, and the lower half of poten- 
tiometer R3. In Fig. 9, CI alter- 
nately charges through Rl and 
Dl and the right-hand half of 
potentiometer R3, and it dis- 
charges through the left-hand 
half potentiometer R3, D2, and 




Dl 






01 



1K> 

1 n 1 6 



+v 



ov 

VaV 
OV 



==BS& 



yvw\^ 



OUTPUT 
AT PIN 3 

OUTPUT 
ACROSS 



-4--SI CLOSED- 
SI OPEN 

b 



- S1 OPEN 



■ 



FIG. 11— GATED 1-kHz OSCILLATOR c 
fering "press-to-turn-on" operatio 
a, CFHB and waveforms at output of pit 
and across CI, b. 



I 



s 

o 

z 

3 

e 
I 

72 



ri : : 

IK-' 



01; 

.01 



+ 5VTO + 15V 
f - 



R2 
75K 



6 



555 



5 
.01 



R3 
10K 



IS1 



■ii ii i 6 



1 



OUTPUT 



' 



- 






































































- 


-*- 


|s, 


CLO! 


>m 











OUTPUT 

AT PIN 3 



FIG. 12— GATED 1-kHz OSCILLATOR of- 
fering "press-to-turn-off" operation, s, 
and waveforms at output of pin 3 and 
across CI, b. 



+ SVT0 + 15V 






Bl 
22K 






01 IK * 




9lsi 



75K 



-CI -i 



ouTPtn 






ri 





■ 


ov_ 


' AV /V -A >-TK 


^^^ N ^X 


T_ Jd 



OUTPUT 
WPIN3 



OUTPUT 

ACROSS 

ct 



Sl OPEN 



-51 CLO 



-St OPEN 



FIG. 13— ALTERNATIVE GATED 1-kHz 
OSCILLATOR offering "press-to-turn- 
on" operation, a, and waveforms at out- 
put of pin 3 and across CI, b. 



R2. Both circuits oscillate at 
about 1.2 kHz with the value of 
CI shown. 



Precision astable circuit 

In the description of astable 
multivibrator operation given 
earlier in this article, it was 
stated that in the first half cycle 
of oscillation timing capacitor 
CI charges from zero volts to 
two-thirds of the supply voltage. 
but in all subsequent half-cy- 
cles it either discharges from 
two-thirds to one-third of the 
supply voltage or charges from 
one-third to two-thirds of that 
voltage. Consequently, the first 
half cycle of oscillation has a far 
longer period than all subse- 
quent half cycles. 



+ 5VTO+15V 



♦ OTTO tl 



r; 



di <: 

(SEE TEXT) ^ 
-M- 

9 °" 
<:R3 



t — t 



HI 

K 



R2 
75K 



555 



sfeC1 ??C2 



.01 



.01 



M 



OUTPUT 



i 






OUTPUT 
AT PIN 3 



— HSI CLOSED |-- 
6 

FIG. 14— ALTERNATIVE GATED 1-kHz 
OSCILLATOR offering "press-to-turn- 
off" operation, 1a and waveforms at out- 
put of pin 3, b. 

In applications calling for a 

low-frequency clock signal, this 
large differential in period can 
cause a timing problem. How- 
ever, this problem can be aver- 
ted by adding an external 
voltage divider and diode as 
shown in Fig. 10. Those compo- 
nents bias CI to a point slightly 
below one-third of the supply 
voltage (rather than zero volts) 
at the moment of switch- on. 
Here, Rl rapidly charges CI to 
one- third of the supply voltage 
through Dl at switch-on, and all 
of the CI charge is subsequently 
controlled by R3 and/or R4 only. 




si OWN 



SI OPEN 



FIG. 15— PRECISION VERSION OF T 
OSCILLATOR in Fig. 13, a, and wa 
forms at output of pin 3 and across C1 



Astable gating 

The 555 in the astable mul 
vibrator mode can be triggen 
on and off in many d iff ere 
ways with either an ele 
tromechanical switch or ; 
electronic signal. The most pc 
ular way to trigger the 555 
through reset pin 4. Figur 
11-a and 12-a show alternati 
ways of triggering the 555 wi 
this pin and pushbutton swifc 

si. 

The 555 is organized so thai 
pin 4 is biased above about 
volts, the astable mode is e 
abled. But if it is biased bek 
0.7 volts by a current great 
than 0.1 milliampere (1 
grounding pin 4 with a res. 
tance less than 7 kilohms. f 
example) the astable mode 
disabled, and the 555s outp 
is biased low. 

For example, the circuit 
Fig. 11-a is normally turned < 
by R3, but it can be turned on 
closing pushbutton switch £ 
which biases pin 4 high. Figu 
12-a shows an astable clrct 
that is normally on, but It ci 
be turned off by closing pus 
button switch SI, which shor 
pin 4 to ground. The circuits 
Figs. 11 and 12 can also be tri 
gered by applying suitable ele 
tronic signals direcdy to thei 



IK!' 






I I 

ci ste c? x 



01 



R2 
75K 



+5VT0 + 15V 



555 






1 



ID11F 



OUTPUT 



MODULATION A 
INPUT 



i 





PULSE WIDTHS VARIABLE 


OUTPUT 
AT PIN 3 




y \ 


% 


k 


















ov- 




















SPACES EQUAL 





FIG, 16— CIRCUIT FOR APPLYING AC- 
COUPLED FM or PPM to a 555 config- 
ured as an oscillator, a, and waveforms 
at output of pin 3, b. 



5V TO + 15V 




FIG. 17— CIRCUIT FOR APPLYING A DC- 
COUPLED FM or PPM to a 555 config- 
ured as an oscillator. 




S.>75£1 
^ TOTAL 



FIG. 18— CIRCUIT GENERATES 800-Hz 
MONOTONE ALARM that operates from 

750-milltwatts. 



. > < . "»"yy 



•yes 
•I70MF 



~i — n 

tn-,: 






■ : « 



1H4001 



m 

1*4001 ■ 

\\ SPKA1 

II 111 



'■mn 



"T *T ^ 



I20O 

Ql 03 i 



FIG. 19— CIRCUIT GENERATES 800-Hz 
MONOSTABLE ALARM. 



tion of CI and R4 close to zero 
volts through R2 preventing os- 
cillation. When pushbutton 
switch SI is closed, Ql is biased 
off, and the astable circuit is 
free to oscillate normally. 

Refer to Fig. 13-b for the wave- 
forms of the circuit in Fig. 13-a. 
When the astable response is 
triggered on, the first half cycle 
is again considerably longer 
than in succeeding half cycles, 
and that the voltage on CI de- 
cays rapidly to nearly zero volts 
when the trigger Is off. Also 
notice that output pin 3 is high 
in the off state. 

Figure 14 shows how the cir- 
cuit in Fig. 13-a can be modified 
to give press- to- turn -off oscilla- 
tion simply by replacing Ql with 
a pushbutton switch. A digital 
signal can trigger this circuit if 
a diode is connected as shown 
in the diagram and the push- 
button SI is deleted. With SI re- 
moved, the circuit will be 
turned off when the input sig- 
nal voltage is reduced below 
one-third of the supply voltage. 
The waveform is shown in Fig. 
14-b. 

Finally, to complete this look 
at triggering techniques, Fig. 




FIG. 20— CIRCUIT GENERATES 800-Hz PULSED-TONE ALARM. 



reset pins. 

In Fig. 11-b, the precise cir- 
cuit waveforms at output pin 3 
and across CI are shown. It can 
be seen that the duration of the 
first half-cycle of oscillation is 
considerably longer than the 
succeeding half cycles because 
of the time for CI to charge to 
two- thirds of the supply voltage. 
Also, note that when the astable 
mode is turned off, the CI volt- 



age decays slowly to zero: the 
output at output pin 3 is zero 
volts in the off condition. The 
waveform characteristics of Fig. 
12-a are similar as shown in Fig. 
12-b. 

Figure 13-a shows an alter- 
native method for triggering the 
555 in the astable mode. Here 
transistor Ql is normally biased 
on by Rl, so it acts like a closed 
switch, which pulls the junc- 



15-a shows how the Fig. 13-a cir- 
cuit can be modified so that the 
duration of its first half-cycle is 
almost equal to that of all suc- 
ceeding half-cycles, thus giving 
precision operation. In the Fig 
15-a circuit, when pushbuttor 
switch SI is open, Ql is satu 
rated, so the voltage dividei 
made up of R2 and R3 pulls th< 
junction of R5 and CI to slightl; 
below one-third of the suppl; 





















^ 


12V TO 


+ 1SV 


R1 - 

iok: 

+ 

% C4 

47G H F 

1 

t 

C1 ? 

10nF 




8 


P3< 
4 10K« K 


7 


8 


D1 
1N40O1 
4 

SPKRlf 

3 ^ l 


D2 -- 

1H4001 


IC2 
555 


IC1 
555 


( 






►R2 
►75K 

. 2 


3 


R4 - 
220K: 


: 


2 




<>R5 

>10K 1 
< 

T 


1 


: R6 < 

M20n 






D3 -. 
1H4Wrr 




' 6 




6 


l. 


s C2; 

.01 








5 

1\ 




Is 






.01 




L/PS ° 1 

^KJ ZN3055 


















. 











FIG. 21— CIRCUIT GENERATES WARBLE ALARM of European emergency vehicles. 



+ 12VTO+15V 



R1 
4.7K 



+ 

%C3 

470pF 




R2 
47K 



IC2 
555 



R3 

4.7K 



Q1 
2N3702 



" 1 _J £HOYU£A_^ 

;' ± 6Q M =< 

5* CI skc2 ^EX. .01 
IOOhF .01 ] 




FIG. 22— CIRCUIT GENERATES SIREN WAIL of police cars. 



charge from an initial valu< 
almost a third of the supply v 
age rather than from zero vo 
Therefore, the duration of 
initial half cycle is similar 
that of all the succeeding 1 
cycles. 

Modulation techniques 

AH of the 555 as table circu 
reviewed so far can be frequei 
or pulse-position modulai 
(FM or PPM) by feeding a si 
able modulation signal I 
control voltage pin 5, whicl 
connected to part of the inter: 
voltage divider chain of the 5! 
The AC modulation signal is 
to pin 5 through a blocking 
pacitor, as in Fig. 16-a, or 1 
DC modulation signal can 
fed directly to pin 5, as shown 
Fig. 17. 

The voltage on pin 5 of I 
Fig. 15-a circuit alters the wic 
of the pulses in each timing 
cle of the 555. but it has alm< 
no effect on the space duratic 
The signal at pin 5 changes t 
PPM pulse width position, 
fecting the total cycle period 
it also influences the output f 
quency, as shown in Fig. 16 
In so doing, pin 3 provides a f 
quency-modulated sign; 
Those characteristics of the 5 
are useful for generating spec 
waveforms. 



<3> 



Q 



Z 

3 

s 
1 

LU 



74 



























\J 


+ 


12VT0 + 


15V 


R1 . 

10K ' 




8 


R4 ; 
4 4.7K - 


i 
i 


•10K ; 


4 


r 1 ^ 

D2 

1N4001 


D3 - 
1N4001 J 


I 






k 7 ■ 


IC2 
555 


IG1 
555 


\ 


SPKR1 




3 


r J 


I R2 
►33K 

* 2 


_3_ 
1 


: rs 

"12K 
Q1 
2N3702 


7 
• R6 
*10OK 

, 2 


3 
1 


I Rfl 
>120U 




04 n 

1N4D(rr 




, 6 


e 


i 










1N4146 

i 

+ 

C3 
470nF 




5 




Is 




(iP 


V 


R7 




JP< 




5 G1 ; 

47|jF 


KC2 
.01 




n 


) 


Z7K 




Q3 i 




L C4- 

] ' 01 1 


^ 


2H3055 










<4 


f 02 
2H3704 





































FIG. 23.— CIRCUIT GENERATES PENETRATING ALARM of Star Trek spaceship. 

voltage through diode Dl, thus the circuit is then free to oscil- 

turning the circuit off. When SI late normally, 

is closed, Ql turns off, Dl is re- Notice in Fig. 15-b that when 

verse biased throuigh R2, and SI is first closed, CI starts to 



Alarms and sirens 

Some of the most popular £ 
plications for the 555 organiz 
as an astable multivibrator £ 
as waveform generators f 
loudspeakers. They can pi 
duce alarm and siren sounc 
Figures 18 to 23 show differe 
ways to create those sounds. . 
of the circuits in those figur 
are triggered by making 
breaking their supply- vol ta 
connections. 

Figure 18 shows an 800-1 
monotone alarm-call generat 
circuit, which can be power 
by any 5- to 15-volt DC supp 
The speaker SPKR1 can ha 
any impedance value. Not 
however, that R x must be win 
in series with any speak 
whose total impedances is le 
than 75 ohms. Select a resist 
to give a total series resistan 
with the speaker of 75 ohm 
continued on page < 



JAMES MELTON 



DO YOU EVER NEED TO POWER 120- 

volt ac equipment when there Is 
no AC outlet available? Our af- 
fordable power inverter was de- 
signed to supply up to 250 watts 
to power line-operated equip- 
ment a a fraction of the cost of 
commercially built units. 

The inverter described here 
has been used to power flood 
lamps, soldering irons (both re- 
sistance and transformer 
types), fans, televisions, and 
portable computers. It has even 
powered an air pump for the au- 
thor's asthmatic son. The inver- 
ter will power almost any device 
that runs on 120 volts AC. Some 
motorized devices won't work 
well, however, A variable-speed 
drill may work, but only at one 
speed. Fans and other purely in- 
ductive loads seem to run at 
about 2 /a normal speed with the 
inverter. Synchronous motors 
will run at normal speed but will 
be a litUe "noisy." 

Power FET's to the rescue 

Power FET (field effect tran- 
sistor) devices have gotten more 
versatile over the last few years 
and, at the same time, the 
prices for them have plumm- 
eted. Nothing can match a FET 
in its ease of interfacing with 
logic signals, and for the ease in 
which it can work in parallel 
with simitar devices without 
the need for any extra compo- 
nents. To parallel the FET's, all 
you have to do is tie the source 
leads together. When the they 
get warm, FET's exhibit a 
positive temperature charac- 
teristic, which means as the 
temperature goes up, so does 
the resistance; as the resistance 
goes up, the current through 
the device is lowered. That 
makes FET's self-limiting when 
working in parallel. 

FET's are now being produced 
with power ratings that can 
often make parallel operation 
unnecessary. The ratings for 
the IRFZ30's that are used in 
this project are amazing: they 
can handle a 30-amp load with 
50 volts across the source-drain 
leads and 75-watt power dis- 
sipation, all in a TO-220AB 



plastic package — for less than 
two bucks each when pur- 
chased in small quantities. 

Operation 

Figure 1 shows the schematic 
of the inverter. A 555 timer, IC1. 
along with R3. R2. and C2. gen- 
erates a 120-Hz ( ± 2 Hz) signal, 
as set by the value of potentiom- 
eter R3. 

The output of IC1 at pin 3 is 
fed to the CLOCK input of a 
CD4013BE dual D-type flip-flop. 
IC2-a, which is wired to divide 
the input frequency by two; that 
generatea the 60-Hz clocking 
for the FET array (91-Q6). The 



output from Hip-flop IC2-a at 
pin I has a 50% duty cycle, 
which is necessary for the out- 
put transformer. The flip-flop 
also provides an inverted out- 
put (q, pin 2), which saves us 
from having to add additional 
components to invert the q 
output. The second half of IC2 
(IC2-b) is not used, so all of its 
input pins are grounded. 

The q and q outputs from IC2- 
a are each fed, via R5 and R4, to 
three inputs of IC3, a CMOS 
CD4050BE hex buffer. Each 
group of three buffer outputs 
drives one bank of FET's in the 
power stage. 



Power small appliances from your 
car or any other 12-volt source 
with our 250-watt Inverter. 

250 WATT 

POWER 
INVERTER 



12VDC- 
130 AC 
INVERTER 




FIG. 1— INVERTER SCHEMATIC. A 555 timer (IC1) generates a 120-Hz signal that is fed 
to a CD4013BE flip-flop (IC2-a) which divides the input frequency by two to generate a 
60- Hz clocking frequency for the FET array (Q1-Q6). 



ft! 



I 



C 

2 

■s 

in 



76 



The inputs to the buffers are 
also controlled by D5 and D6, 
which are connected to the drai- 
ns of the FET's so that the array- 
that is turned-on essentially 
has control of the drivers of the 
opposite array. When one side Is 
turned on and its drain is at 
ground potential, the other side 
cannot turn on because the in- 
put to the buffer for that array is 
also being held at ground. It 
stays that way until the control- 
ling array has completely 
turned off and the drain voltage 
has gone above about 6 volts. 
That is necessary because the 
turn-off time for a FET is longer 
than its turn-on time. If the di- 
odes were eliminated, both ar- 
rays of FET's would be turned 
on simultaneously during each 
transistion, which creates tre- 
mendous spikes on the battery, 
the equipment tied to the out- 
put of the inverter, and to the 
FET's themselves. 



The FET array can be made as 
big or as little as your applica- 
tion requires. The author 
needed at least 250 watts, and 
used two IRFZ30 s in parallel for 
each array. However, to play it 
safe, use three in parallel (or 
however many you need) for 
each array as we've shown in 
the schematic. Diodes D4 and 
D3 dampen inductive kickback 
from the transformer winding 
that would likely cause over- 
heating and premature tran- 
sistor breakdown. 

Power-supply conditioning 
circuitry (Dl, Rl, D2, and CI) 
eliminates spikes, overloads, 
and other noise from a car's 12- 
volt supply. Even though the 
555 can handle up to a 15-volt 
supply, power-supply spikes will 
surely damage it. 

If the transformer you use has 
a center tap, the center tap must 
be connected to the 12-voIt line 
and the two 12-volt windings 



must be connected to the dra 
of their respective driving tr; 
sisters. The author usee 
Jefferson buck/boost traj 
former that's normally used 
reduce or increase the line v< 
age for AC devices. If you ; 
going to buy a transformer, y 
can use any center-tap 24-v 
or dual-winding 12-volt trai 
former. It is important to us> 
transformer that can supply t 
ammount of current that yc 
application requires. 

Construction 

Some of the componen 
mount on a small PC board. 1 
which we've provided the ft 
pattern. The parts-placeme 
diagram is shown in Fig. 2. ^ 
recommend that you use soc 
ets for the IC's. After solderii 
all components on the boar 
apply 12 volts and measure tl 
frequency on the pads mark' 
J4 and J2. Adjust R3 for a rea 







— ~h 




(SQUARE WAVE) 








L-. 7 


□ 





; WINDING TWO 

• 



a 




» WINDING ONE 

• 



Q3 



D4 



Q6 



D3 



S1 



+ 12V 
FROM -*- 
CAR 
BATTERY 



FIG. 2— MOST OF THE COMPONENTS mount on a small PC board. The off-board 
components can be mounted on a terminal strip or perforated construction board. 



ing of 60 Hz, and make sure the 
voltage is very close to '/a of the 
supply voltage on each pad. 
That tells you that your duty cy- 
cle Is 50%. 

Now connect the rest of the 
components. The small off- 
board components can be 
mounted on a terminal strip. 
However, be sure to mount the 
FET's on a heatsink. If the heat- 
sink is at ground potential, also 
be sure to insulate the FET's 
from it. 



rato-^-^Tr^ 






T 



1 




|n— a d — c ¥ 

a 



LZJ 



r 



-olo n lnooc 



FOIL PATTERN for the inverter board. 



PARTS LIST 

All resistors are Vb-watt, 5%, un- 
less otherwise noted. 

R1— 60 ohms, 1 watt, 10% 

R2— 33,000 ohms 

R3— 50,000 ohms, 10-turn potenti- 
ometer 

R4, R5— +700 ohms 

Capacitors 

CI— 220 (j.F, 35 volts, electrolytic 

C2 — 0.1 |aF. 50 volts, ceramic disk 

Semiconductors 

IC1— LM555 timer 

IC2— CD4013BE CMOS dual D- 
type flip-flop 

IC3— CD4050BE CMOS hex buffer 

D1, D3, D4— 1N4001 diode 

D2— 1N4751 13-volt Zener diode 

D5,D6—1N914 diode 

Q1-Q6— IRFZ30 30-amp, 60-volt 
FET 

Other components 

T1— Jefferson #216-1121 buck/ 
boost transformer (contact WW 
Granger, Inc., 1250 Busch Pkwy, 
Buffalo Grove, IL 60015, 
708-459-5445) or other 12- or 24- 
volt center-tapped transformer 
(see text) 

S1—SPST switch 

F1 — -20-amp fuse (or use value ac- 
cording to desired output current 
and transformer used) 

Miscellaneous: fuse holder, cab- 
inet, mounting hardware, AC out- 
let, car cigarette lighter plug, wire, 
solder, etc. 




FIG. 3— THE PROTOTYPE INVERTER. 
The author used a car cigarrette lighter 
plug on the end of the power-input lead 
and an AC outlet for plugging appli- 
ances into. 




FIG. 4— THE FET'S ARE MOUNTED on 
metal plates used as heatsinks. If the 
heatsink is at ground potential, insulate 
the FETs from the heatsink. 

The author used a car ciga- 
rette lighter plug on the end of 
the power- input lead, but you 
are free to use alligator clips or 
whatever is most convenient for 
you. A standard AC outlet was 
mounted on the front panel of 
the unit. The prototype was In- 
stalled in an old, rugged metal 
case, but you can use whatever 
you have on hand. Figure 3 
shows the prototype inverter 
and how everything is as- 
sembled. Figure 4 shows a 
close-up view of the FET's and 
how they are mounted on metal 
plates used as heatsinks. 

Operation 

To operate the unit, plug the 
input power into your cigarette 
lighter socket, turn on the 
power switch, and turn on the 
appliance that's plugged intc 
the inverter. When you are no1 
using the inverter, be sure tc 
turn it off, since the trans- 
former will draw about 2 amps 
even with no load. That wi] 
drain your car battery fairlj 
quickly! R-J 







i*li'H'im'M»il 




Syndicated Reviewers, AM Stereo, and Consumer Fraud 



LARRY KLEIN 



Si 



& 
p 



§ 



78 



I've frequently been distressed 
by the writings of the syndicated 
audio columnists, the pundits 
whose opinions appear weekly in 
large and small local newspapers, 
I've met many of them over the 
years and, by and large, they are 
nice people, but I just don't like the 
job they do. What's wrong? Several 
things, 

I feel strongly that a writer should 
not express his opinion in print on 
the audio qualities of a borrowed 
product listened to under uncon- 
trolled conditions in a home environ- 
ment. Such home evaluations 
without lab test backup are, in gen- 
eral, untrustworthy. They actually 
tell you far more about the writer's 
mood, health, and relationship with 
the manufacturer than they do 
about the product. This is not to say 
that some of the recommended 
products aren't topnotch, but the 
reader has no way — sound un- 
heard — of confirming the reviewer's 
opinions. 

Am I being too harsh in my judg- 
ment? 1 think not. The temptation to 
say nice things about a product be- 
comes intense when a writer has 
been personally wined, dined, 
junketed, and brainwashed by a 
company's public relations agency. 
I can say that in the 35 years or so 
that I've been writing about audio 
I've kept my skirts relatively clean. 
Despite temptations to do other- 
wise, I have never confused my sub- 
jective opinions with objective facts 
and never praised a hi-fi component 
in print without a lab test backup. I 
should admit that as the technical 
director of the world's largest cir- 
culation audio magazine, I found it 
easy to be holier than almost any- 
body. I regularly received such man- 
ufacturer-supplied perks as all- 
expense-paid annual trips to audio 
shows and factories in Japan, Eu- 
rope, and elsewhere, and all the 



long-term-loan audio equipment I 
could use without extolling the vir- 
tues of anyone's products. Free- 
lance writers, on the other hand, 
inevitably find themselves in a quid 
pro quo situation. The amount of 
laudatory "ink" they give to prod- 
ucts in their columns correlates di- 
rectly with the frequency of invites 
to press junkets. Their columns and 
comments are reprinted by gratified 
manufacturers, and they are on the 
"A" lists for goodies. 

Once 1 left Stereo Review for the 
freelance life, my invitations slowly 
dwindled as the various PR agen- 
cies became aware of my new unex- 
alted status. I could have reversed 
the situation somewhat by taking 
the same product review route as 
my syndicated contemporaries, but 
I chose not to do so. In any case, to 
reaffirm my point: Be careful before 
committing your dollars on the basis 
of any opinions unsupported by lab- 
oratory testing. It's just too easy to 
be mislead, 

AM stereo 

Remember AM stereo? It's an 
idea that won't die — but won't 
come fully to life either. Perhaps a 
dozen years ago, when AM stereo 
was first introduced as a new broad- 
cast technology, I wrote that be- 
cause of the lack of consumer 
interest the format would probably 
never ffy. The letters of disagree- 
ment that subsequently reached my 
desk were mostly from station 
owners, broadcast engineers, and 
companies with investments in AM- 
stereo technology. 

For years there was no visible 
progress on the AM-stereo front, 
possibly because the FCC in its 
wisdom Cha!) decided to let the 
competing formats fight it out in the 
marketplace. True, there was an oc- 
casional press release telling of this 
or that company's home or car re- 



ceiver's having AM-stereo rec 
tion facilities, usually Motoro 
system. 

A mini breakthrough almost 
curred in June 1990 when the 
tional Association of Broadcast 
(NAB) and Denon announce 
"comprehensive component brc 
cast monitor tuner that does it ; 
The "all" included the now-defi 
FMX FM noise-reduction systt 
AM stereo (Motorola's C-Qua 
and the newly promulgated NR 
AM standard. The new standarc 
eluded an extension of the AM 1 
ing range C520 to 1710 kHz), a | 
emphasis/de-emphasis curve, . 
a wider, tightly specified audio be 
width. The tuner was promised 
"early 1991." 

I recently called the Denon te 
nical rep to ask what, if anyth 
had happened to the tuner. He fa 
me a copy of a press release da 
May 1992 announcing a revii 
tuner that no longer had FMX 
did have AMAX, which seems tc 
the NRSC parameters under a r 
name (See Radio-Electroni- 
February 1 992 for more details). ' 
AM bandwidth can be switchec 
wide or narrow, providing either 
broadest audio-frequency respo 
or the lowest noise. Helping to 
duce AM impulse noise is a no 
blanking circuit from Sprague/^ 
gro Microsystems. 

I found the tuner's technical S| 
sheet, which was printed in Jar; 
to be somewhat puzzling. The at 
frequency response of the - 
tuner set to wide is given as 50 
to 7.5 kHz, +1.5-3 dB. Certa 
that's better than what one find 
most AM/FM receivers, but it I 
far short of CD quality. 

The claim has been made t 

good AM stereo is frequently in 

tinguishable from FM, That may 

be, given the aging ears of the c 

continued on page 



HARDWARE HACKER 



Histogram equalization, alternate action latches, gamma curve 
correction, digital image processing, and semiconductor IC houses. 



DDK LANCASTER 



Stop the presses. Murata has 
just announced a Gyrostar 
piezo gyroscope. Which, if it 
is as great as it looks, could easily 
become the hacker component of 
the decade. All I've got on this so far 
is that brief note in the June 8th 
Design News and a promise for 
more technical information. Need- 
less to say, the hacker potential of a 
$5 navigation gyro would be truly 
revolutionary. 

Be sure to stay tuned on this one. 

Things are also starting to happen 
fast and furious on that direct-toner 
printed circuit board front. Since my 
last report, the new water-soluble 
decal-based Toner Transfer System 
offered by DynaArt has been further 
improved. The new Printed Circuit 
Board Transfer Film from Techniks 
looks even more promising. 

What Techniks did was take their 
old differential transfer system and 
add a new blue polymeric release 
coating. The polymeric release 
coating can dramatically improve 
the transfer; it actually becomes an 
important part of your resist pattern. 

Faster than light? 

Every week or so I get at least 
one letter or helpline call from peo- 
ple who feel they have clearly 
broken some physical law. Maybe 
they have proof that the speed of 
light is not a constant. Or that those 
three laws of thermodynamics just 
do not apply to them. Or that per- 
petual motion can be possible using 
magnetic repulsion. Or they have 
tapped the zero point scalar energy 
from the fabric of space. Or that 
their latest pet theory proves the 
cold-fusion process. 

Usually, they'll also complain that 
they've sent their theory every- 
where and have gotten no replies. 
Or that they are getting ignored be- 
cause they are outsiders. 

Very often, their inquiries will be 



self-defeating. How? They will in- 
clude totally irrelevant religious or 
political contexts. Or they'll be 
super secretive. Or written and sub- 
mitted in such a way that they 
scream "Hey, kick me, for I'm not 
even computer literate." 

If it likes water, looks like a duck, 
and quacks like a duck... 

But consider who is receiving 
those letters. Based on past experi- 
ence, the editors or the publishers 
know that the probability is 0,99 + 
that the lab work (if any) is just plain 
wrong. Or, more typically, not even 
wrong. And 0.99+ that the sendee 
is clearly a few chips shy of a full 
board. Why should they believe 
you? 

The sad thing is that needle in the 
haystack. I'm going to be generous 
and claim that one letter in 500 in 
fact does have the germ of a new 
theory or a developable product or a 
fresh look at a solvable problem. 
And, yes, newer ideas often will get 
ignored or vehemently attacked. 

What can you really do if you have 
genuinely beaten those overwhelm- 
ing odds and your controversial idea 
is in fact both new and for real? 

There are two possible routes you 
could take to get your ideas accept- 
ed. The first or real science method 
is to thoroughly try and prove that 
you are wrong. Be sure to use lots of 
careful research, especially through 
Dialog and those UMI reprints. Be 
certain to subscribe to all of the rele- 
vant insider trade journals and go 

NEED HELP? 



Phone or write your Hardware 
Hacker questions directly to: 

Don Lancaster 

Synergetics 

Box 809 

Thatcher, AZ 85552 

(602) 428-4073 



out of your way to study the schol- 
arly publications in the field. Learn 
all the lingo. Attend conferences 
and trade shows. Find a patient and 
knowledgeable industry insider that 
is willing to look at your idea and 
comment honestly on it. 

Be absolutely certain that you 
have a simple experiment that can 
be independently duplicated and 
verified by disinterested outsiders. 

Hire some competent engineer- 
ing or physical science consultants 
to study and add credibility to all 
your claims. Take enough college 
and university level courses to make 
sure you do thoroughly understand 
at least the fundamentals of the 
field — -along with the needed math 
to back it up. 

And finally, present the ideas 
clearly identified as a possible new 
theory in some professional contex' 
totally free of religious, political, oi 
any conspiracy mumbo jumbo. 

The second route is to publish vi< 
a pseudoscience press. There are 
quite a few underground and altei 
nate life publications that welcom* 
material of this type. Every now an< 
then, Whole Earth Reviewgtves yoi 
a list and rundown of all the maga 
zines of that genre. Let me know 
you want to see a resource sideba 
on those. 

One leading bookstore that doe 
specialize in selling and distributin 
pseudoscience topics is High Ene 
gy Enterprises. Many of their offe 
ings are utterly fascinating. Thos 
folks also sponsor several year' 
forums where controversy 
pseudoscience topics are strong 
encouraged. 

Several very important tips whe 
publishing your own pseudoscienc 
tracts; Be sure to use cut-and-pas 
Xerox-of-a-Xerox and lots of poor 
printed sloppy layouts. Smeared it 
on cheap paper is a must. Free 
quote obscure rural newspapers ; 



your prime data sources. Include il- 
legible artwork. Extensively refer to 
unheard-of and unavailable journals. 
Use plenty of irrelevant inference 
and innuendo. 

Use only 20-200 year old refer- 
ences, especially in any rapidly 
changing field. Misquote and drop 
some big names, even if totally out 
of context and they never heard of 
you. "Billions and billions of Carl 
Sagan's ago..." Never offer any 
succinct and easily verified experi- 
ment. 

Always use ten words where one 
will do. Make all of your paragraphs 
unbearably wide and long. Then run 
them all together in haphazard 
order. Never come right out and 
state your key points. Work Tesia in 
somehow, and be sure to include 
plenty of obscure religious and/or 
political references. Show how your 
theory is now being suppressed by 
a federal conspiracy headed by the 
Trilateral Commission and secretly 
funded through both the WCTU and 
theSPCA. 

Ignore all the personal computers 
entirely. They are only a passing fad 
that never will catch on. Finally, do 





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A 



+V o 




o-o +v 



_. Clear 
(A) Relay converted to latch. 



10K 
-Wr 

10K 



3_ Clear 5. Set 



(B) Inverter pair used as latch. 



22K 
-WrV 



•W 



470K 
Change ^ 1flF 

(C) Alternate action pushbutton. 






FIG. 1— SOME SIMPLE LATCHES and 
alternate action circuits. 

not ever, under any circumstances, 
use any new desktop publishing 
tools and techniques. 

Alternate action switches 

I got a helpline call the other day 
asking for a circuit to convert any 
old ordinary relay into an alternate- 
action on-off device. Well, as the 
caller has found out on his own, that 
gets a little trickier than it sounds. 

Figure 1 -a shows how to convert a 
regular relay into a latching relay. 
Press normally open button A and 
your relay pulls in. The pull in closes 
a relay contact that holds the relay 
engaged. To reset the relay, press 
normally closed button B. The relay 
drops out, opening its latching con- 
tact. This is a simple example of a 
latch, or a sef-nssef flip-flop. 

In Fig. 1-6 we've used a pair of 
digital logic inverters instead. An in- 
verter outputs a one for any zero 
input and vice versa. Assume the 
left inverter happens to be output- 
ting a one. The right inverter sees 



this one as an input, and output 
zero. The zero in turn read 
around and holds the left inverte 
its present state. We are tl 
latched and stable. Press butto 
to set your latch. Press button E 
clear your latch. 

It turns out that any alternate- 
tion circuit has to consist of j 
distinct storage elements. One 
for "Where am I?" and one is 
"Where was I?" If you don't prov 
two storage devices, you will ■ 
into major reliability, oscillation, 
preferred state hassles. 

In most integrated circuits, 
two needed storage elements 
done with a pair of separate latch 
One is called the master flip-fl 
The other is the slave flip-flop. Of 
they are combined into a sin 
more complex logic block, formin 
rype-D clocked flip-flop or so 
similar device. 

Check carefully, and you will e\ 
find that the button on a retracta 
ball-point pen consists of two c 
tinct storage devices. 

The simplest alternate-acti 
pushbutton I know of appears in F 
1-c, The "Where am I?" stora 
consists of that pair of back-to-b; 
inverters. The "Where was I?" si 
age is the capacitor. 

Here's how it works: Some bi 
time after that latch changes, I 
capacitor will charge up to hold i 



The VALUE at each PEL or picture eleme 
determines the brightness for that pel; th< 
LOCATION of that pel in the array sets 
the pel position in your actual image. 




107 206 03^Wl93 2S* '" 091 

080 128 219M29)177 161 - 253 

101 223 115 216 015 041 ■■■ 251 

083 205 001 240 032 089 ■■■ 093 

032 093 170 079 093 106 ■■■ 115 

119 023 126 194 091 086 ■■■ 004 



FIG. 2— A DIGITAL IMAGE is nothing t 
an array of numbers. Digital image pi 
cessing takes those numbers and 
places them with other numbet 
following a rule or set of rules. Wh 
there is a stunning variety of uses t 
digital Image processing tricks ai 
techniques, two of the most import: 
involve gamma correction and hisi 
gram equalization. 



® 



Typical Gamma curve of a CRT electron beam 
display or a "white write" laser printer will 
wash out many of the lighter whites. 

(B) Properly gamma corrected display or printer 
treats all gray levels equally. Some available 
gray levels may be lost In the process. 

(5) Typical Gamma curve of a "black write" laser 
printer {such as a Canon SX) will muddy the 
darker grays. 



(white) 



Perceived 

gray levels 

at output 



(black) 




Intended gray fevels at input 



FIG. 3— THE GAMMA CURVE for any display or printer relates how the brightness 
levels are viewer perceived compared to how they are input. A non-linear gamma 
either "muddies the lows" or "washes out the highs." Gamma correction attempts to 
make each gray equally significant to the end viewer. 



"Where was i?" one or zero. Press- 
ing the button forces the "Where 
was I?" value back onto the input of 
the first inverter, and the latch quick- 
ly flips. 

That happens because the 
charge on a capacitor cannot 
change immediately. Thus, at the in- 
stant the switch is closed, the ca- 
pacitor acts as a very low 
impedance which "force feeds" its 
value to the inverter input. As soon 
as the inverters flip, positive feed- 
back reinforces and holds the new 
value. 

Releasing the button will let the 
"Where am I?" pair of inverters 
work normally, A short interval later, 
the capacitor will charge up Cor 
down) to its new "Where was I?" 
value, and the cycle can repeat. 

The circuit can also be used as a 
relay driver. It's the fastest and best 
way I know of to make a mechanical 
relay reliably alternate its states. 
While any old CMOS gates could 
be used, my favorite here would be 
a 74HC13 hex Schmidt trigger. 
Much more technical information on 



counters, latches, and state alterna- 
tion appears in my CMOS Cook- 
book. 

Digital image processing 

I never cease to be amazed at 
how stunningly versatile that 
PostScript general-purpose lan- 
guage is. I've recently used 
PostScript to create a group of 
rapid, easy, and fun digital image 
processing tools. The tools and a 
few test images to go with them 
have been posted to my CEnie 
PSRT RoundTable as IMAGE- 
KIT PS. 

What I'd like to do here is give you 
a brief introduction to digital image 
processing. We'll limit ourselves to 
high-quality gray-scale images. 

We will also try to zero in on doing 
both a gamma correction and a 
histogram equalization. Those are 
both highly important and little un- 
derstood crucial uses for serious 
digital image processing. Fail to un- 
derstand either one and your im- 
ages will all end up as disasters 
waiting to happen. 



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We'll first note that good old sil- 
ver halide "slopping-in-the-slush" 
photo work is both incredibly ver- 
satile and highly forgiving — besides 
having an enormous dynamic range. 

Instead, electronic digital dis- 
plays, printers, and any photoset- 
ters demand data which is always 
"right on." If anything misses at all, 
you will get lousy to useless results. 
That's why digital image processing 
has become so important. And so 
hackable. 

Hmrnm. To do some digital image 
processing, you have to start with a 
digital image. You can borrow one of 
mine off of GEnie PSRT, or grab one 
from a scanner, off a satellite, a fax 
machine, or a video-capture board. 
Such a digital image is made up of 
picture elements, or pets. Note that 
a pel may or may not be the same 
size as the final pixel on your output 
device. A pel is simply the minimum 
resolvable data value found in your 
numbers within the digital image. 

In a gray scale image, a pel gets 
defined by three parameters. The 



pel luminance value will tell you how 
bright th\s tiny portion of your scene 
will be. Its X position value will tell 
you how far over in the picture this 
pel sits, while its Y position tells you 
how far up and down. 

Ferinstance, in the LENA.PS file 
#463 on up PSRT, we use 256 pos- 
sible grays (ranging from 
PostScript's = black smoothly up 
on through a 1 = white). These pels 
are arranged as an image 256 bytes 
wide by 192 bytes high. That size 
was picked to be big enough to be 
useful and interesting, yet small 
enough, short enough, and fast 
enough to have lots of fun with. 
PostScript, of course, can handle 
any image size and resolution you 
want. 

The first byte in your data file con- 
tains the 8-bit luminance value for 
the upper lefthand pel. The second 
byte is for the next pet to the right, 
and so on. After 256 horizontal 
pels, the data starts over again at 
the left pel of the next line down. 
This repeats for a total of 192 lines 



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or 49152 bytes. Or 48K for short. 

As Ftg. 2 shows us, digital image 
processing simply consists of tak- 
ing this large array of digital bytes 
and then creating a second array of 
new digital bytes. The bytes m the 
second array are related to the 
bytes in the first array by some rule 
or set of rules. And your processed 
new image should somehow be 
"better" for whatever you are trying 
to do. 

For instance, we might just take 
each individual data value and make 
it larger. That would brighten your 
display and give you lighter values. 
Make each data value smaller, and 
you will instead darken your display, 
Favoring darker values. 

Should there be any defect in the 
picture, you can "retouch" by look- 
ing at adjacent pel values and work- 
ing out some type of average. 
Carried to extremes, this sort of dig- 
ital image processing can remove 
telephone poles from pictures, rear- 
range trees, and literally leap tall 
buildings with a single bound. 



A digital image processing anti- 
aliasing trick lets you remove the 
jaggies from black and white lines. 
For anti-aliasing, gray values should 
get substituted equal to the ex- 
pected average value at each pel. 
From any reasonable viewing dis- 
tance, your jaggies will magically 
disappear. 

Calculating new pel values based 
upon values of neighbor pels opens 
up all sorts of powerful digital image 
processing opportunities. Ferins- 
tance, if you average or low-pass 
fitter against nearby pels, you can 
soften or soft focus your image. If 
you emphasize differences, you can 
crispen or sharpen your final image. 
Carried to extremes, a crispening or 
sharpening becomes edge detec- 
tion, where only outlines remain. A 
magic algorithm called a Laplacian 
is often used for high-quality edge 
detection. 

What if your original picture is out 
of focus or blurry? Well, you can go 
to a rather fancy Fourier or wavelet 
transform into a transform plane 



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Gray 



usage 



(black) 



Gray levels 



FIG. 4— THIS STOCK "LENA" DIGITAL IMAGE appears rather FIG. 5— HISTOGRAM EQUALIZED "LENA" DIGITAL IMAGE 

"weak" or "low in contrast." A glance at the histogram clearly much higher contrast. The histogram shows all gray values a 

shows why. There are no dark blacks, no lighter whites, and the full use. A full histogram equalization is the equivalent 

few remaining grays cluster around the two peaks. perfect photo darkroom "dodge and burn." 



Si 



1 



c 
p 



84 



and extract a deblurring function. 
Which can cancel out much (but not 
all) of such things as camera mo- 
tion. And perform such tricks as 
reading those license plates on 
speeding cars. 

There are now zillions of exciting 
techniques which use digital image 
processing. We may look at some 
of these in future columns. But the 
first of the two techniques I feel are 
by far the most important involves... 

Gamma correction 

The eye acts as a log, rather than 
a linear device. And deep down in- 
side, most display schemes are also 
quite nonlinear. As Fig. 3 shows us, 
the Gamma curve for any imaging 
system relates how the expected 
input gray levels actually appear to 
your eye at the output. 

The process of "fixing" a gamma 
curve is called Gamma Correction. 
On a video display, nonlinearities 
are purposely introduced to attempt 
to cancel out such nonlinearities as 
the square law response of most 
electron beams to a control voltage. 
In color work, the strengths of each 



individual beam are also carefully 
adjusted to make each color appear 
to be equally bright. Even if the color 
phosphors used have different sen- 
sitivities. As does your eye. 

If at all possible, you want to do 
your gamma correction in someway 
that does not cut into the number of 
grays you have available. But if it 
simply can't be helped, digital image 
processing can be applied to gam- 
ma correct your display. It can do 
that by redefining gray levels, trad- 
ing off a lot of nonlinear grays for 
fewer and more linear ones. 

All of today's laser printers have 
inherently nonlinear gamma curves. 
This happens because a round dot 
is used which has to be larger than 
the intended square pixel it is sup- 
posed to completely and flawlessly 
cover. Thus, in a black write system 
(such as the Canon SX) where the 
laser places down black dots, typ- 
ical gray levels usually end up darker 
than you asked for. 

The PhotoGrade system used on 
the Apple LaserWriter G uses dig- 
ital image processing to trade off its 
gray levels for a more linear gamma. 



We saw some details on 
PhotoGrade halftoning process 
month. At 106 DPI, Apple's F 
toGrade system has 1 28 gray le 
available. A total of 61 of these 
often used for gamma correct 
The gamma correction redefi 
lots of really dark grays and a fe* 
the mid range grays. The net re 
is the remaining 67 distinct and i 
Gamma corrected grays. 

The PhotoGrade system of 
you three calibration options, 
options compensate for your 
ticular choice of toner, density 
tings, humidity, and so on. C 
calibration, a coarse and a finer 
tone square are put down for ty| 
gray levels. This is done for tl 
different pages. You then pick 
page you like the best. The inte 
code does a predefined Gar 
correction for you. 

Additional details on PhotoGi 
processing appear in my Gi 
PSRT#451 LASGCAL.PS and' 
in #388 LASGNOTE.TXT. / 
quite handy is a #R023I 
LaserWriter fig Printers Devek 
Notes from APDA. 









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Histograms 

Those photo darkroom techni- 
cians and artists have lots of secret 
tricks they use to explore the in- 
credible dynamic range of photo 
film. By lengthening or shortening 
all their exposures, they can make 
all of their prints darker or lighter. By 
printing on a "soft" paper, they can 
reduce their dynamic range and 
contrast. Or increase it by using a 
"hard" paper. Or eliminate it entirely 
with a "litho" photo paper. 

Even more sneaky is dodging and 
burning. With dodging, you put your 
moving and out-of-focus hand or a 



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dodging paddle between the en- 
larger and the area being printed. 
That holds back your light in a se- 
lected area and makes that area 
lighter than normal. Which lets you 
pull details out of any dark or "mud- 
dy" areas of your negative. 

With burning, you hold an opaque 
mask having a small, ragged, out of 
focus, and rapidly moving hole in it 
between your enlarger and the print 
paper. Burning lets you darken your 
highlights and extract details from 
underexposed areas. 

By now, most of you have seen 
those spectacular Navajo slot can- 



yon photos. Most any southwest 
calendar should include at least one 
example. And Arizona Highways will 
be happy to sell you bunches of 
them. These incredible prints carry 
dodging and burning to an extreme, 
using multiple exposures and twen- 
ty or more very precisely aligned 
dodging masks to bring out the sub- 
tleties of color and texture. 

Digital image processing can be 
used to imitate these darkroom 
tricks. And getting things right on 
gets even more important with dig- 
ital images, because you will always 
be severely limited by both the dy- 
namic range and laser resolution. 

The first step in correcting a dig- 
ital image is to find out what was 
wrong with it in the first place. To do 
this, you run a histogram. A histo- 
gram is simply a vote on how many 
of the grays get used how often. 
Figure 4 shows us the stock and 
well-known Lena digital image, 
which should appear slightly 
"weak" or low in contrast. 

That histogram underneath Lena 
clearly shows us why Those light- 
est and darkest grays are not used 
at all. And most of the rest fill two 
clearly defined peaks. 

A digital image processing meth- 
od known as histogram equalization 
will let you perform a magic dodging 
and burning that can often dramat- 
ically improve your results. In Fig. 5 
you see a much higher contrast and 
greatly improved Lena with lots 
more "snap." 

To do your histogram equaliza- 
tion, you try to spread all of your 
pels around such that each gray 
gets used neady as often as any 
other. You can then selectively re- 
place each pel with a lighter or a 
darker gray, adjusting your accumu- 
lated sum to spread out the total 
number of pels per gray. 

In short, you'll do an absolutely 
perfect dodge and bum. 

For instance, if you have 49152 
pels in your image and use 256 gray 
levels, you redefine your grays to 
get about 192 or so pels per gray 
level. A simple accumulated running 
average does the job for you. Full 
code details in my digital image 
tools on GEnie PSRT, especially IM- 
AGEKIT.PS. As you can see in Fig. 
5, nearly all of those available grays 
are fully and uniformly used. 



By doing a histogram equaliza- 
tion, you can print "auto shopper" 
quality images on any unenhanced 
300 DPI laser printer. 

Figures 4 and 5 are available as 
PSRT files #463 LENA.PS and my 
#468 LENAHIST.PS. 

Semiconductor chip houses 

I have been meaning to do some 
resource sidebars that give you 
most integrated circuit manufac- 
turers, or at least the more hacker- 
friendly ones- Since there's so many 
of them, we'll need several sidebars 
to do the job right. So, Actel through 
Fujitsu will appear this month, and 
I'll show you the rest of them as we 
get to them. 

Some data books are free. 
Others have "optional" pricing de- 
pending on whether the sales per- 
son likes you or whether any of the 
covered chips are currently being 
promoted. For others, just about ev- 
erybody has to pay the going rate. 

Your best bet is to first request a 
short form catalog, a price list, and 



their technical literature and applica- 
tion note index. These are all usually 
both free and immediately available. 
Be sure to use your laser-printed 
letterhead or a professional sound- 
ing telephone request. 

New tech lit 

Data books include the 
Optoelectronic Products Catalog 
from Quality Technologies. This 
used to be the old GE/Harris opto 
line. 

Advanced Linear Devices has a 
Product Databook on linear timers, 
op-amps, and comparators. 

From Signetics/Philips, there's a 
new data book on CMOS Se- 
quencer Solutions. And from 
Hitachi, there's a Semiconductor 
Devices for Communications data 
book. Included are lots of telco and 
cellular radio devices. 

Our two brand new labor-of-love 
newsletters include WeatherSat Ink 
and the Geo-Monitor. The first is on 
weather satellite image reception; 
the second on earthquake monitor- 



ing and prediction. 

Over in our neat mechanic, 
department, a free sample of 
machined plastic is availabli 
KMC. And an incredible c 
from Ou (water Plastics. Thes 
are laboring under the delusit 
they are now in the store < 
fixtures business. In reality, tl 
fer lots of useful new electror 
prototyping hardware at unbe 
prices. Not to mention off- tl 
ideas. They even stock GreciE 
for writing odes on. 

For the two key books or 
the fundamentals of digita 
grated circuits, try my C 
Cookbook and TTL Cookbo 
ther by themselves or as part 
Lancaster Classics Library. 

As usual, we've gathered it 
the resources mentioned to> 
into either the Names & Numt 
the Integrated Circuit Mai 
turers sidebars. Check thes 
before you use our no-charge 
nical helpline or call for yoi 
hacker secrets brochure. 




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Let's see what's involved in d esc rambling a SSAVI signal. 

M II III ■ 






1 



88 



Fooling around with the simple 
video stuff we've been build- 
ing is a nice alternative to 
hanging around on street corners, 
but it's not really all that terrific if 
your ultimate goal is to figure out 
what to do with the junk that shows 
up on certain channels on your TV. 
Suppressed sync is the Model-T 
version of video scrambling, and 
you can bet your bottom dollar that 
things have gotten a lot more com- 
plicated. Enter the digital age. 

Since the suppressed-sync 
scrambling system was so simple, it 
wasn't long before people with only 
moderate electronic skills figured 
out what was being done and how to 
beat it. Even the simple stuff we put 
together over the last couple of 
months could — with some minor 
additions— do the job. As the cable 
business grew, so did the complex- 
ity of their scrambling methods. 

As I told you when we first started 
out on this trip into cable video land, 
ripping the video signal apart is 
easy — putting it back together suc- 
cessfully is something else entirely. 
The amount of messing up that's 
done to the standard video signal is 
directly proportional to the cost. 
More intense scrambling is more 
expensive. Cable operators have to 
balance their degree of security 
against the cost of the equipment. 
Also, the larger the customer base, 
the less expensive the scrambling 
system has to be. In New York City 
(and other large areas), the cable 
companies have a lot of subscrib- 
ers, each of whom needs a cable 
box. The more boxes the cable 
company has to buy (they don't 
make them themselves), the more 
money it has to keep tied up in its 
inventory. 

The old suppressed-sync system 
was a one-way deal. If you got a box 
that could descramble one channel, 



it could descramble any channel. 
Which channels would be un- 
scrambled was determined by one 
of the wafers on the channel selec- 
tor dial. A position would be either 
jumped or open, which was a major 
cable company headache for two 
reasons. The first was that they had 
to open the boxes and solder or cut 
traces to configure the box for a 
given customer. The second was 
that some enterprising people real- 
ized what was going on. opened up 
their cable boxes, and reconfigured 
it themselves. 

The only way the cable compa- 
nies could guard against that was to 
use screws with oddball shaped 
heads to hold the box together. 
When that didn't work, they started 
using screws that had a left-hand 
thread. But enough history. 

What the cable companies 
needed was a way to talk to each of 
the boxes individually, while they 
were in customer's homes. Making 
such addressable boxes also meant 
that several scrambling methods 
could be used; the boxes could be 
told which method was in use at any 
one time. Since that information 
could be sent to the box during the 
vertical blanking interval (while the 
beam was off the screen), the cable 
operator could change the scram- 
bling method from field to field- — up 
to sixty times a second. The boxes 



/001XEIV 



could also keep a serial numl 
an EPROM or some other st 
device, which meant that t 
could be addressed individual I 
the descrambling circuitry col 
turned on and off for separate 
nels from the main cable con 
office. The cable companies 
it. 

Understanding that kind of s 
a bit more difficult than the ok 
pressed-sync system, but i 
take the pieces one at a time 
gets cut down to manageable 
sized chunks. Although the 
company's scrambling deliver; 
tern became much more sof 
cated, it was still faced witi 
same cost restrictions when i 
to decide which of the ava 
scrambling techniques to use 

One of the most popular ch 
was the so called SSAVI sy 
That's an acronym for Sync 
pression Active Video Inversi 
allows the video to be deliver 
your doorstep in one of four Ae 

• Suppressed horizontal syni 
normal video (Fig. 1). 

• Suppressed horizontal syn> 
inverted video (Fig. 2). 

• Normal sync and suppresse 
eo (Fig. 3). 

• Normal sync and normal 
(we can forget this one). 

Before we get into the nitty 
of the SSAVI system, there 



oixe ,sv 

~V0tt£O v- 




|-« CONT/tOL. JU- 



-P/CTi/X.E- 



FIG. 1— THE SSAVI SYSTEM can deliver video with suppressed horizontal syr 
normal video. 




OIAE .IV- 
-403XE OV- 



FIG. 2— SUPPRESSED HORIZONTAL SYNC and inverted video Is also possible with 
the SSAVI system. 



This isn't as strange as it might 
seem. In a normal video signal, the 
reference for color is the burst sig- 
nal that follows horizontal sync. The 
colorburst signal lasts only a bit lon- 
ger than 2 microseconds, but it's 
used as a reference for the whole 
video line, which is about 63 micro- 
seconds long. As far as color cor- 
rection is concerned, that means 
there's no real reference signal avail- 
able for more than 95% of the line! 
The color phase for the rest of the 



few basic things you should know, 
because they tell you some interest- 
ing things about how the system 
works. 

The first is that horizontal sync is 
never inverted — even if the picture 
is inverted. This means that any cir- 
cuit designed to descramble it has 
to separate the two basic parts of 
the video line (control and picture 
first). We have to be able to turn the 
picture right side up Cif needed) 
without inverting the control section 
as well. 

The SSAVI system seems even 
more complex when you realize that 
the job of separating control and 
picture has to be done on lines that 
might very well have no horizontal 
sync pulse that can be used as a 
reference mark. In the older sup- 
pressed-sync system, the sync 
could be recovered from the gating 
signal that was buried in the audio; 
with the SSAVI system, there's 
nothing like that available. 

The key to regenerating the video 
signal is based on the fact that all 
aspects of it are tied together in a 
strict mathematical relationship. If 
you can locate one part of the sig- 
nal, you can determine where every- 
thing else has to be. 

The broad picture for a de- 
scrambler, therefore, is to design a 
circuit that can identify one part of 
the signal, and then use the repeti- 
tion of that signal as a reference for 
restoring the rest of the video. You 
should realize by now that we're 
talking about a phase-locked loop, 
or PLL Even if the identifiable com- 
ponent of the video occurs only 
once a field Cor even once a frame), 
that's still often enough to control 
the frequency of a voltage-con- 
trolled oscillator, or VCO, and lock 
the PLL to the received video. 



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FIG. 3— HERE'S WHAT NORMAL SYNC and suppressed video look like. 



line is based on the stand-alone 
3.58-MHz generator that's a normal 
part of the TV set. 

Building a SSAVI descrambler 
isn't as easy as building one to take 
care of suppressed sync, but it's not 
as difficult as you might think. Be- 
fore we start to work out the details 
of the circuitry, we have to draw up a 
comprehensive list of exactly what 
we want the circuit to do. A circuit 
designed to descramble the SSAVI 
system needs the following basic 
features: 

• A means of knowing if the picture 
will be normal or inverted. 

• The ability to generate horizontal 
sync pulses. 

• A way to identify a definite point 
in the received video. 

• A circuit to place horizontal sync 
pulses at the right point. 

Some SSAVI systems also play 
games with the audio, but the meth- 
ods used to hide the audio have 
been around for a long time. The 
audio is usually buried on a subcar- 
rier that's related, in some mathe- 
matical way, to the IF component of 
the TV signal. We'll get into that 
briefly when we take care of restor- 
ing the picture. 

Although we'll be working out the 
details of the circuitry next time, you 
should already have some ideas of 
what it has to be like. The SSAVI 
system uses digital signals for se- 
curity and access rights — the stuff 
that cable executives lie awake all 
night thinking about (instead of less- 
important things such as improving 
picture quality, increasing channel 
services, and widening the audio 
bandwidth. Because the first step in 
handling SSAVI scrambled signals 
is to locate a known point in the 
signal, we'll be using counters and 
other standard digital logic to keep 
track of where everything is sup- 



posed to be. That's right peoc 
most of the guts of a SSAVI i 
scrambler are made of the sa 
standard digital stuff we've be 
using in this column since the bet 
ning. 

In the future we'll take apar 
typical frame of SSAVI-encoc 
video and see how we can pu 
back together again correctly, 
not as complicated as you think a 
to tell you the truth, f wouldn't b 
bit surprised if a bunch of you re, 
ers beat me to it. In the meantir 
to help you appreciate what's 
volved in scrambling a video sigr 
next month we'll work on some 
cuitry that will scramble a perfec 
good video signal. I 



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COMPUTER CONNECTIONS 




Miniature multimedia machines. 



JEFF HDLTZM AN 



Apple has indeed announced 
a second miniature multi- 
media machine (MMM), as 
rumored here last month. Newton, 
the first MMM, will be designed and 
produced in conjunction with Sharp 
Electronics, and is more computer 
than gadget. Sweet Pea, the sec- 
ond, will be designed and produced 
in conjunction with Toshiba, and is 
more gadget than computer. 
Whereas Apple has publicly shown 
the hand-wired Newton prototype. 
Sweet Pea appears to exist only at 
the conceptual level. Nonetheless, 
the implications and technology be- 
hind Sweet Pea are enormous. 

Newton has no keyboard, but 
uses a stylus for input. Connectivity 
to other Newtons. and to PC's and 
Macs, is also strong. The point is to 
service students, executives, facto- 
ry workers, and others who need 
on-the-go computing that inte- 
grates smoothly and cleanly with 
desktop systems and networks. 

Sweet Pea, on the other hand, 
appears to be aimed squarely at the 
consumer market, in particular, a 
segment that some are calling by 
the awkward term infotainment, 
which attempts to combine learning 
and entertainment. Sweet Pea will 
play specially prepared CD's con- 
taining text, graphics, audio, and 
video. According to one Toshiba of- 
ficial, it may connect to a TV set for 
home use, or it may be portable. It 
should hit the shelves in summer of 
1993, and should be priced under 
$1000. 

The software technologies be- 
hind Sweet Pea are mighty interest- 
ing. Kaleida, the joint venture in 
multimedia between IBM and Ap- 
ple, will supply these technologies. 
One is called Script X; it is an author- 
ing language that developers can 
use to create multimedia titles that 
will run on multiple platforms, includ- 
ing Intel and Motorola CPU's, and 



RISC devices. It will also run on spe- 
cial operating systems used by 
MMMs. In fact, Kaleida is develop- 
ing one such operating system, the 
Consumer Operating System 
(COS) that will, of course, support 
Script X. Script X is also slated to 
support Apple's multimedia stan- 
dard, QuickTime. 

Apple has signed deals with 
Warner New Media and Paramount 
Communications to supply titles; 
Claris, Apple's software subsidiary, 
will also develop new titles. 

Kaleida got off to a slow start, and 
has been partially eclipsed by other 
more immediately apparent benefits 
of the historic 1991 accords be- 
tween IBM and Apple. However, the 
recent appointment of a board of 
directors, along with Nat Goldhaber 
as head of Kaleida, not to mention 
the Sweet Pea technology an- 
nouncements, all indicate that Ka- 
leida is likely to be the vortex of 
some fascinating and industry-shak- 
ing new developments. 

Less technologically advanced, 
but likely to have some market im- 
pact, are new pen-based pocket or- 
ganizers that will be introduced by 
Sharp and a joint effort between 
Tandy and Casio. At an estimated 
$300, the Tandy/Casio unit aims to 
undercut initial pricing on Newton 
and Sweet Pea devices. The Tandy/ 
Casio will use the GeoWorks graph- 
ical environment, will have built-in 
handwriting recognition, and will 
have a PCMCIA slot for memory 
and telecommunications. Look for it 
sometime in 1993. The Sharp unit 
adds pen input to the Wizard line, 
and includes an extensive pushbut- 
ton/menu-based interface. Pricing 
was unclear as of press time; the 
device is scheduled for release this 
year. Also scheduled from Sharp is 
an 8088-based palmtop that should 
sell for about $1000. 

Microsoft is hankering after this 



market as well. Lately there has 
been discussion about a CD-ROM 
based machine that would run a 
ROM-based subset of Windows, 
connect to a TV set. and provide 
infotainment. Apparently designed 
to compete in the video-game mar- 
ket, the device is currently going by 
the name Wintendo. 

Upheaval in the PC business 

In the beginning was the PC, 
which meant an 8088 and one or 
two 360K floppies. Then came the 
XT, which added a hard disk and 
bumped memory up to 640K. Next 
came the AT, which added a full 16- 
bit processor and peripheral inter- 
face. Then came the 386. which 
brought 32-bit processing and un- 
heard-of performance. For a good 
four or five years, the boundaries 
between those four divisions were 
clear. However, in the past two 
years, the introduction of new 
CPU's by both Intel and its rivals has 
almost completely obliterated 
those bounds. Now there is a 
smooth spectrum of often overlap- 
ping price/performance choices 
ranging from lowly 386SX's to 50- 
MHz 80486DXs. It's nearly impos- 
sible to keep in mind all the varia- 
tions among CPU's, including 
speed, bus width, power manage- 
ment, cache size, math 
coprocessor, and system support 
components. Choosing a complete 
system is no longer a choice among 
four well-defined categories. 

Against that backdrop, manufac- 
turers find it difficult to make their 
offerings stand out. In the past year, 
intense price wars have forced sys- 
tem costs to absurdly low levels. At 
first, the price wars were conducted 
almost exclusively among clone 
manufacturers, but Compaq re- 
cently joined the fray, IBM has 
promised to do so by this fall, and 
second-tier suppliers like Del! have 



Si 

i 



e 

ijj 



92 



already retaliated. One industry 
analyst has stated that there are 
some 500 PC suppliers, of which 
450 shouldn't exist. Another ana- 
lyst suggests that within a few 
years, the vendor base will be re- 
duced to a dozen multinational cor- 
porations that supply 95% of 
industry needs. 

Another trend is that toward in- 
creasingly dense integration, both 
at the chip and the system level. For 
example, the original PC used 16K 
DRAM's, Today's standard is 4 
megabits, an increase of 256 times. 
Back then, system logic was built 
from hundreds of discrete TTL com- 
ponents. Today, three or four VLSI 
IC's do the same job. At the system 
level, many motherboards today 
contain built-in serial and parallel 
ports, hard- and floppy-disk control- 
lers, and expansive memory — 16 
megabytes or more. By contrast, 
original IBM motherboards seldom 
held more than 51 2K of memory, 
and contained nothing but the re- 
quired system logic. 

Together, price wars and the 
larger trend of increasing integration 
lead to the necessity of product dif- 
ferentiation, or some means of mak- 
ing your product stand out in the 
customer's mind from that of your 
competitor. Price cutting is one way, 
but it can only go so far. The other 



way is to add features, and that's 
what we'll start seeing this fall- 
Look for systems with built-in net- 
working and sound capabilities. 
Look for systems from IBM and 
others with preinstalled operating 
system software (OS/2, DOS/Win- 
dows). Look for systems with tons 
of bundled applications. Look for 
creative marketing schemes. (For 
example. DAK. a mail-order house, 
now gives away a 386DX/33 with 
purchase of $1500 worth of soft- 
ware — and quality stuff at that, in- 
cluding current versions of Win- 
dows, Word for Windows, Norton 
Desktop, Adobe Type Manager, Par- 
adox, and more). Look for pre- 
assembled networks supporting 
anywhere from 2 to 250 users. Look 
for hard-drive upgrades from Sea- 
gate and others with preinstalled 
software (Windows). Look for laser- 
printer upgrades that include RAM 
with font and emulation cartridges. 
Look for operating systems (Win- 
dows and OS/2) to include more 
and more features traditionally as- 
sumed to be part of the applications 
realm, e.g., networking and E-mail. 
The following tire several trends 
to watch: 

CPU Wars 

Intel continues to try to fend off 
attacks on its 386 business — AMD 




FIG. 1— LOCAL BUS ARCHITECTURES supplied by Intel and the Video Electronics 
Standards Association (VESA) promise to provide a high-bandwidth channel between 
the CPU and fast peripherals including video and network adapters, and mass- 
storage interfaces. 



expects to take 50% of the mar 
by the end of this year — but b 
AMD and Cyrix are mounting r 
offensives on the 486. Cyrix will 
troduce 25-, 33-, and 40-MHz ■ 
sions of its 486 clone at about I 
the price Intel charges. Meanwf 
AMD plans similar introductio 
but a recent legal setback co 
stall its efforts. IIT is also enter 
the race; the company stated 
cently that it is developing a * 
clone with integrated video disf 
and image compression hardwt 
paralleling Intel's efforts to comb 
an X86 CPU with IBM's XGA gra 
ics and Intel's own Digital Video 
teractive (DVD, a digital system 
compressing and playing back > 
eo on standard PC's. Timely ini 
duction of the latter could be 
breakthrough PC-based multime 
has been waiting for. 

Intel's P5 (sometimes known 
the 586, although reports indie 
that Intel is searching for a n 
name) contains two CPU's, a 4! 
compatible unit, and a Reduced 
struction Set Computing CRIE 
unit. What's the value of sticks 
RISC chip in a PC? On the otl 
hand, what would be the value 
sticking a 486 in a workstation (r 
mally powered by a RISC chip)? I 
PC, let the 486 do PC things (DC 
Windows, OS/2), and let the Rl: 
unit run the video system or a d€ 
cated compression/decompn 
sion unit. In a workstation, let i 
RISC unit do Unix things, and let ■ 
486 provide PC compatibility. 

Power Play 

Power consumption is becom 
a hot topic not only among nc 
book PC vendors, but among de 
top system vendors as we 
Consumers demand longer batt 
life from their notebooks— a m 
mum of eight or ten hours. Deskl 
vendors need to cut power c< 
sumption for reasons of energy c< 
servation. Significantly reduci 
energy consumption by compuh 
would save $1 billion per year, p 
reduce C0 2 emissions by the eqi 
alent of 5 million automobiles dur 
the same period. Achieving the 
reductions is not wishful thinkinc 
recently formed industry/gove 
ment coalition that includes I 
EPA, Apple, Compaq, DEC, 1 



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IBM, NCR, Zenith, and other man- 
ufacturers announced a set of de- 
sign parameters centered around 
several types of "sleep" modes and 
3.3-volt system components. The 
goal is to reduce power consump- 
tion of the average PC to 30 watts. 
AMD is promoting 3-volt system 
design guidelines, and it says that a 
complete PC chip set will be avail- 
able this summer, with product in- 
troductions (probably centered 
around notebooks) scheduled for 
fall COMDEX. To support this bur- 
geoning market, Intel has an- 
nounced a 3.3-volt version of the 
386SL that includes a fully static 
CPU, cache controller, bus and 
memory controllers, that can inter- 
face with both 3.3- and 5-volt pe- 
ripherals. Cirrus Logic has intro- 
duced a dual-voltage video control- 
ler. 

Just Add Water 

Networking is not yet fully per- 
vasive. However, new chip designs 
promise low-cost system additions 
that will further spread the ability to 
link up. One study shows steady 
growth in units shipped peryear dur- 
ing the period 1989 (2.2 million) 
through 1995(6.7 million). AMD has 
introduced a single-IC Ethernet 
adapter that (along with similar de- 
vices from National, SMC, and 



others) is going to further increase 
the availability and use of networks. 
The chip will be a built-in component 
on many new motherboards; sev- 
eral influential PC systems houses 
(Apple, Compaq, Dell, HP, North- 
gate) have already introduced (or 
will shortly) systems with built-in 
network adapters. Couple that with 
increasingly aggressive marketing 
by Novell, plus built-in network ca- 
pabilities of the next version of Win- 
dows — and you've got instant 
networking. 

The Magic Bus 

Windows and OS/2 demand fast, 
high-performance computers. As 
clock speed increases, getting data 
in and out of the CPU becomes 
more critical to maximizing system 
performance. Our trusty old system 
buses (ISA, EISA, MCA) simply 
aren't up to the task. In recent 
months, computer manufacturers 
have added a local bus that provides 
a direct path between the CPU and 
some other component, usually a 
special video adapter. So far, how- 
ever, these efforts have been ham- 
pered by a lack of standards. 

In response, Intel and an industry 
consortium called the Video Elec- 
tronics Standards Association 
(VESA) have each devised its own 
local bus standard (see Fig. 1). 



Some published reports have 
claimed that the two standards will 
compete with each other; however, 
Intel officials have stated publicly 
that the two efforts are complemen- 
tary. Both share throughputs in the 
120-130 megabytes-per-second 
range. The VESA spec includes a 
connector design (based on a Micro 
Channel bus connector) that the In- 
tel spec currently lacks. On the 
other hand, the Intel spec includes a 
special interface IC that helps iso- 
late the CPU from I/O sub- 
systems — and that presumably 
allows for transparent CPU up- 
grades via the company's Over- 
Drive technology. Due to bus-timing 
and signal-reflection issues, local 
bus slots will most likely be limited 
to three, e.g., one each for video, 
network, and hard-disk control; the 
latter could be a SCSI host adapter 
for connecting multiple devices. The 
regular expansion bus would then 
be limited to slow-speed devices. 

In short, the next few years will 
see many PC vendors dropping out; 
the ones that remain will be fighting 
tooth and nail to establish their 
products with increasingly dense in- 
tegration of hardware and software 
components. Price wars are already 
raging; feature wars are just about 
to break out. This is going to be one 
heck of an interesting battle. R-E 



HANDI TALKIE 



continued from page 60 



Si 

I 
8 

5" 

a 



9 
1 

LU 

94 



ed, variable Polyswiteh resistor 
R30 could trip and/or the out- 
put power MOSFET's could 
overheat. 

When using the flexible "rub- 
ber ducky" antenna, it might be 
necessary to fine tune capacitor 
C30, taking care to keep the an- 
tenna away from people or large 
metal objects. 

After tuning the transmitter, 
set up the receiver. Turn the 
power on and set the squelch 
control fully counterclockwise 
(off). With the 32-ohm speaker 
connected, increase the volume 
until the background noise is 
audible. Using the oscillocope, 
look at the output from 
recovered audio pin 16 of the 
FM receiver chip IC3, and adjust 
inductor L10 so that the signal 
reaches a maximum level. 

If an FM-modulated RF source 
is avaliable, connect it to the an- 
tenna jack and set it to a 1 mi- 
crovolt output level. Set the 
audio signal to 1 kHz and the 
deviation to 4 kHz. Adjust L10 
for a symetric waveform on pin 
16 of IC3. The tone should be 
audible in the speaker. Set the 
input level to 0.3 microvolts and 
adjust L3 for minimum noise 
level. (This adjustment is op- 
tional.) 

The range of the transceiver 
with the specified antenna is 
one to three miles, depending 
on background noise and the 
proximity of buildings or geo- 
graphical obstructions. The 
range can be increased with a 
citizen band (CB) base station 
antenna, or if its transmission 
frequency is set for the 10-meter 
amateur radio band and a suit- 
able antenna for that frequency 
range is connected. 

To change the transceiver's 
frequency from 25 MHz to 31 
MHz, change crystals 1 and 3 
(XTAL1 and XTAL3) and tune 
the transceiver according to the 
instructions given earlier. (See 
the Parts List for the crystal 
specs.) To operate the trans- 
ceiver outside of the 25-MHz to 
31-MHz bands, the transmit fil- 
ter as well as the multiplier com- 
ponents must be changed. R-E 



VERSATILE OSCILLATOR 



continued from page 74 



That resistance value will keep 
the peak speaker currents with- 
in the 200-milliampere output 
limit of the 555. The output 
power of this alarm circuit de- 
pends on speaker impedance 
and supply voltage, but it can be 
as high as 750 milliwatts with a 
75-ohm speaker and a 15-voit 
supply. Notice that C3 ia an elec- 
trolytic capacitor. 

Figure 19 shows how the out- 
put power of the circuit in Fig. 
18 can be boosted to several 
watts with buffer transistor Ql. 
The resulting high speaker out- 
put current can introduce a sig- 
nificant ripple voltage to the 
power source. Diode Dl and 
electrolytic capacitor C3 protect 
the 555 from the effects of that 
ripple. Diodes D2 and D3 clamp 
the inductive switching spikes 
from the speaker and protect Ql 
against damage. The circuits in 
Figs. 20 to 23 have a similar 
output stages. 

Figure 20 shows how a pair of 
555s organized as astable mul- 
tivibrators form an 800-Hz 
pulsed- tone alarm generator. In 
this circuit IC1 is wired as a 
500-Hz alarm generator, and 
IC2 is wired as a 1-Hz oscillator 
that triggers IC1 on and off 
through diode Dl once per sec- 
ond, thus generating the pulse- 
tone alarm. 

The circuit in Fig. 21 gener- 
ates the penetrating two-tone 
"he-haw" sound of European 
emergencyvehicles. Here, IC1 is 
also wired as an alarm gener- 
ator, and IC2 is wired as a 1-Hz 
oscillator. But in this case the 
output of IC2 frequency modu- 
lates IC1 through resistor R5. 
The output frequency of IC1 al- 
ternates symmetrically between 
500 Hz and 440 Hz in one-sec- 
ond alternating cycles. 

Figure 22 shows a circuit that 
generates the wailing noise of a 
police siren. Here IC2 is wired as 
a low-frequency oscillator with a 
cycle period of about 6 seconds. 
The slowly varying ramp wave- 
form of IC2, buffered by emitter 
follower transistor Ql. frequen- 
cy modulates alarm generator 
IC1 through resistor R6. In this 



circuit IC1 has a natural cei 
frequency of about 500 Hz. 
alarm output signal starts 
low frequency, rises for tf 
seconds to a high freque; 
then decays over a perio( 
three seconds to a low-freqi 
cy before repeating itself as 1 
as power is applied. 

Finally, the circuit in Fig 
generates an alarm that sii 
fates the "Red Alert" that is o 
heard in the Star Trek TV ser 
The sound starts at a low 
quency and rises to a high 
quency in about 1.15 secor 
ceases for about 0.35 secor 
and then starts rising ag 
from a low frequency. H 
again, the sound pattern 
peats as long as power is app 
to the circuit. 

The 555 labeled IC2 is w: 
as a non-symmetrical oscilla 
Capacitor CI alter n at 
charges through Rl and di 
Dl, and discharges through 
The result is a rapidly rising ; 
slowly falling "sawtooth" w; 
form across CI. After buffet 
by Ql, this waveform freque 
modulates pin 5 of IC1 throi 
R7, causing the output frequ 
cy of IC1 to rise slowly dui 
the decay part of the sawto 
waveform and to colla] 
rapidly during the rising pai 
the sawtooth waveform. 

The rectangular waveforn 
pin 3 of IC2 turns IC1 
through common-emitter < 
plifier Q2 during the de 
phase of the alarm, Therefi 
only the rising parts of 
sound pattern are heard wh 
sound very much like the £ 
Trek Red Alert. 

The outputs of most of the 
cuits in this article have b 
taken from output pin 3, 
many of the figures hai 
shown triangular wavefor 
developed across the timing 
pacitor (e.g. Figs. 3b, lib, 
and 15b). There might be oc 
sions when you will find th 
sawtooth (or ramp) wa 
useful. You can obtain a s 
tooth by tapping the cha 
voltage across the timing car 
itor. By charging the capac 
with a constant-current sou 
instead of a simple resistar 
the ramp can be made quite 
ear. 



Countersurveillance 



Never before has so much 
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Foiling Information Thieves 
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The professional discussions seen 
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AUDIO UPDATE 



continued from page 78 



sical-music audience and the poor 
audio quality of most FM broad- 
casts. In any case, the question re- 
mains: Is the listening public really 
interested in AM stereo? 

I don't relish raining on anyone's 
parade, but I suspect that (to mix a 
metaphor) the AM-stereo band- 
wagon will never get off the ground. 

Consumer fraud? 

One of the panel discussions at 
last fall's Audio Engineering Society 
convention was titled "New Cable 
Designs: Innovation or Consumer 
Fraud?" The organizer of the event 
was strongly anti-cable and had 
stacked the panel accordingly. One 
of the surprising guests was 
Wilfredo Lopez, a non-audio person 
from the New York City Department 
of Consumer Affairs. He presented 
his department's view about what 
constituted fraudulent advertising, 
and suggested that most audio 
components are "blind" items, 
meaning that the average consumer 
is not in a position to judge the valid- 
ity of advertising claims. Deceptive 
practices include "false implica- 




The AMAX logo will identity AM re- 
ceivers that meet the NRSC require- 
ments. 

tions of quality or characteristics of 
the item." Mr. Lopez went on to say 
that if his agency finds stores trying 
to sell a speaker cable that is heav- 
ier but not better — but they are nev- 
ertheless claiming it is — it might 
take action against them. 

I would caution Mr. Lopez to tread 
carefully In any area where consum- 
ers are being sold "dreams" — prod- 
ucts that purport to make them 
slimmer, younger, more beautiful, or 
their equipment better-sounding — 
they don't want to be told that they 
are being deluded. For example, the 
cosmetic industry would seem ripe 
for such an investigation with its cel- 
lulite removal creams, skin re- 
juvenators and other such products. 
Is it a defense or justification for the 
manufacturer to say that the con- 
sumer "thinks" the product works, 
notwithstanding objective evidence 
to the contrary? 

In truth, it had never occurred to 
me that the absurd claims made by 



many high-end cable and accessi 
manufacturers could be legally i 
fined as fraudulent. In the years tl 
I've been dealing with audio eqL 
ment claims, I never became vi 
upset by the sometimes technic; 
off-the-wall — or at least unprover 
pronouncements of the vario 
manufacturers. As a matter of fac 
even had a hand in writing some e 
and technical papers for varic 
companies promulgating th 
sometimes strange technologi 
points of view. 

Because the literature was airr 
at a high-end audience, I felt no g 
at providing the kind of nonser 
they loved to hear. After all, I 
tionalized, it wasn't as though 1 
outrageously priced equipment v 
depriving anyone's wife and child] 
of food. 

My ultimate conscience-clear 
maneuver was to editorialize unc 
my own name against some of I 
properties (ultra-wide bandwid 
olefin cable insulation, dua!-pov 
supplies, etc.) that I had extollec 
the ads. In any case, I took (and s 
take) none of this very serioui 
and I regarded my jabs and jibes 
audiophile nonsense as editorii 
interesting but not really powei 
blows for truth, justice, and I 
American Way. I 



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RESTRICTED technical information: Electronic 
surveillance, schematics, lock smithing, covert 
sciences, hacking, etc. Huge selection. Free 
brochures. MENTOR-2, Drawer 1549, Asbury 
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ENGINEERING software and hardware, PC/ 
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layout, FFT analysis, mathematics, circuit 
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JERROLO, Tocom and Zenith "test" chlpj 
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!3 K 



DIGITAj METERS AND CQUHTERS KIT ASSEMS 



SU-A3 3 >Muh>Kne;<n«.idl3F'U .*UScHUiruii|AA 3*» 4J00 

5U-U ' 'iP:i|^DFv AAA i! K U(f 

914* J^H'PTMSWOdDFU IwAftSpUiKuuiAAA 4130 5200 

SViS 3-:«iiHhFi.-1t:*<U(LCDDHP f* Hcs funnel- AA X00 « U 

SU 100 !»MCChB.H>Nqjr»evCwri[i AA.A F^DD HOD 



METAL CABINETS WITH ALUMINUM PANEL 



M0C41 

LB 1 173 

UVtBH 

ufl-ue.5 

I'j l«J 



match Vi r-n ;.f 

TA 7100 FA-37TA TAJflB ?J |fi 

T1WS3* TA-JJ7A TAilffl ?B SO 

: TA-JH7 Fiisoa TA1?QUK7 FA-M0UK? TA lOOO* 34 SO 

, TA-4T7 TA-flOOMH TA.tSOO. TA 1O0W TA MX 3B00 

ia 3^,-a ia reoo i'a ;:k ■* i;cm«: »so 



POWER TRANSFORMERS 



C*SCFtlPTi0N W*rCMih|0 PB.CJ 

2I^*;BAB30Vir?« FAMOUK? TA-StH TA 5«W TA IJW 7(00 

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JWsZfiA, r*.i!OM« U0O 

JlVs7M IMS5I T.PM 

■ifv.J l J :-]!■;* 1 r CO 

.iWliZBA FA-3BDa 4$ 00 



Wt *^:*fH r-jiat O*ot C*03 fcis«*i Cw«n indOi#c*n- Wtinflby DPSgreuoa 
■nsdl uS imrn S*M; una lAp Dr U» "»' Butfcria US Ptaa*? m* a^ Htoi 
pt5*nrr*ifi3fp«inriov«rJ , lb» orlwiDR'OrOKX » Al fliMn&ed u"*|triaf»*30fllVl 
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MARK V Kl,i:c I RONICS. INC. 

ORDER IN CALIFORNIA 1-8Q0-S21-MARK 
ORDER OUTSIDE CA 1-B00-423-FIVE 
CATALOG & INFORMATION (213) 888-6988 
ORDER 8Y FAX (213} 888-686B tj-E3 

SIM') K. SIuumiii \n-, \ limit Ih-IIi .. [\ '«ir.4il 



CIRCLE 93 ON FREE INFORMATION CARD 



CB RADIO OWNERS! 



We specialize in a wide variety of technical 
information, parts and services for CB radios, 
10-Meter and FM conversion kits, repair books, 

plans, high-performance accessories. Thousands 
of satisfied customers since 1976! Catalog S2. 



CBC INTERNATIONAL 

P.O. BOX 31500RE. PHOENIX. AZ 8S04G 



PROTECT yourself and equipment from electrical 
shacks. Complete unit $98.95, SAFETY-UN- 
LIMITED, 1743 Baldwin Road, Yorktown, NY 
10598. S'H S5.00. 

CABLE equipment at wholesale prices, Tocom, 
Oak, Zenith, Jerrold, S.A., Hamlin, add on de- 
scramblers, test chips, all fully guaranteed. 
S.A.C. 1 (800) 622-3799. M-F 7A-3P PST. 

TV conv/descrambler specials. DPV $189.00, 
RTC-56 S99.O0, Tocom-VIP S250.00, S.A, 85XX 
series $169.00, Zenith $199.00, Hamlin 66O0-3M 
$79.00, full warranty. MOUNT HOOD ELEC- 
TRONICS (206) 260-0107. 

PCB: Printed circuit board art work made to your 
specifications plotted on transparency. Multi layer 
and surface component capable. Circuit board 
production available, free estimate send sche- 
matic to NEGRON ENGINEERING, 159 Garfield 
Place, Brooklyn, NV 11215. Fax (718) 768-4028. 

PLATED thru hole printed circuits. $25 00 mini- 
mum. Fast turnaround. For more information call 
A.P. CIRCUITS, (403) 250-3406 or BBS (403) 
291-9342 {8,n,1), 



WIRELESS CABLE RECEIVERS 1.9 TO Z.7 GHz 



30 CH PAHACOl IC DISH SYSTI M SI 73 .90 

3D CH BOO AN If UNA SYSTEM SI 93.90 

30 CH CRYSTAL CDNTROIUJ D SYSTEM S3M .95 
SUK MICROWAVE INTL. INC. SEND I1.M FOR 
f 0. B0I a Mi!? CATALOG OH THESE 

FHOEHK . U. S5W7 I.N D 1 H E 5 FJN E 

ISO?) 130-1145 VIDEO PRODUCTS 

OUAimTYOISCOUMTS 
■HfllMU MHHIII CM •!» 



D 



CABLE Stealth: protect yourself from de- 
scrambler detection and stop the "bullet." Preset/ 
tested, only $24.99. $4.00 S&H, BALDWIN 
ELECTRONICS, Box 9291. Baltimore. MD 
21222-0291. 

LASERS, light shows, plans, books, 5mw to 20 
watts, free catalog call 1 (800) 356-7714 or write 
MWK IND„ 198 Lewis Ct, Corona, CA 91720. 

IS it true... Jeeps for $44.00 through the U.S. 
gov't? Toll free 1 (800) 467-8585 or (504) 
649-5745 ext. S-5192. 

JERROLD Impulse digital converter. Upgrade 
your 400 450 unit to this latest system. (212) 
898-8819. 



ANTIQUE RADIO CLASSIFIjED 
Free Sample! 

Antique Radio's 
Largest Circulation Monthly, [Bf© ). 
Articles, Ads & Classifieds. 
6-Month Trial: $15. 1-Yr: $27 ($40-1st Class}. 
A.R.C., P.O. BOX 802-L9, Carlisle, MA 01741 




THE best multiplex stereo FM transmitter on the 
market, use any audio source and enjoy crystal 
clear FM reception from any receiver in your home 
or yard. The JC2010 kit is pre tested and only 
requires your final assembly. $99.95 plus $2.50 
S&H check or money order. No CODs. JCB INC., 
7239 Valley St., Dalton Gardens, ID 83814, (208) 
772-9207. 

GENERAL Instrument DPV-7's $250,00, Scien- 
tific Atlanta 8500's $150.00, Tocom's $150.00 to 
$250.00. CABLE WORLD, 1 (800) 234-7193. 



TEST equipment pre-owned now at aflor< 
prices. Signal generators from $50,00. 
cilloscopes from $50.00. Other equipment in 
ing manuals available. Send $2.00 U.S 
catalog refunded on first order. J.B. Et 
TRONICS, 3446 Dempster, Skokie, IL 60 
(708) 982-1973. 

CABLE TV converters. Jerrold, Zenith, Pio 
Oak, Scientifi c Atlanta, and many more. 12 ) 
experience gives us the advantage. Vise 
Amex COD ADVANTAGE ELECTRONICS, I 
1 (800) 952-3916 1125 Riverwood Dr.. Bums 
MN 55337. 




GREAT Project, Silent 
reminds you when yen 
get. SSTSn (Turn Sigiu 
minder) beeps 3 seci 
after 15 seconds. Cyc! 
peats until cancelled. Unobtrusive, disabled when bra 
Compact kit mounts atop flashar. Parts, case, PCB, ! 
maNc. instructions (15 PPD: 2/525: 3/J30. Vlsa/MC, 
brochure 1-800-398-5605. Prewired 120 PPD: 2435; 3 
Silent Sam, 1627 Bis [I Dr.. Columbus, OH 43227 



PLANS AND KITS 



FASCINATING electronic devicesl Daz 
Lasers! Transmitters! Detectors! Free ene 
Tesla! Kits/assembled! Catalog $4.00 (refui 
ble). QUANTUM RESEARCH, 17919-77 / 
Edmonton, AB. T5T 2S1 . 

HOBBY/broadcasting/HAM/CB/surveillar 
transmitters, amplifiers, cable TV, science, b 
other great projects! Catalog $1.00. PANA 
Box 130-F1O, Paradise, CA 95967. 

DESCRAMBLER kits. Complete cable kit $+< 
Complete satellite kit $49.95. Add $5.00 shipj 
Free brochure. No New York sales. SUMMIT 
Box 489, Bronx. NY 10465. 



REMOTE CONTROL KEYCH/ 

■ Complete Wflrsiw-rrswrr 

.■'■iB/.iirid'+JivtJ&RFJrw 

Fully eansmbifMi iri#uefirifi:p 

to : bul.ld. yo u r owrv : » ut t> i* 






w 



Visffectfr 
:{51D) 651, 



.><;**. yo A*j:sJjBnip 

/^ 5 @:Sl9.95, 10t§> $14 
C... Box 141 56, Fremont, Cb 94! 

1425 Fex (510) 651-3i 



SURVEILLANCE transmitter kits tune fror 
to 305 MH^. Mains pov.'ered duplex, telepfi 
room, combination telephone/room. Catalog 
Popular Communications, Popular E 
tronics and Radio-Electronics book review 
"Electronic Eavesdropping Equipment 
sign," $2.00. SHEFFIELD ELECTRONICS, 
Box 377785-C, Chicago, IL 60637-7785. 

FREE! Sensational catalog of fun kits. I 
TECHNOLOGIES, 20993 Foothill Blvd., S 
307R. Hayward. CA 94541-1511. 

TEST-Aids for testing units in full servive m< 
Starcom VII. $40.00: Starcom VI, $30.00; I 
com DPBB, $50.00; Pioneer, clears error cc 
f£2 E3 F_4 E5. $75.00; Pioneer cubes, will not , 
internal serial number, $175.00; Tocom 
5503/5507. $25.00; S.A. 8500, $25.00; 8 
$30.00; 8580, $40.00; 8570/90, $50.00; Ze 
ZTAC, $25.00; security tools and remotes. 
ENGINEERING, (617) 770-3830. 

DESCRAMBLING, new secret manual. E 
your own descr amblers for cable and subsc 
tion TV. Instructions, schematics for SS AVI, g. 
sync, Sinewave, (HBO, Cinemax, Showti 
UHF, Adult) $12,95, $2.00 postage. CAB 
TRONICS, Box 30502R, Bethesda, MD 208 

WIRELESS guitar transmission system. B 
your own for $39.95! (kit) RADIOACT 
TRANSMISSIONS 1 (800) 263-9221 Ext. 25 

ETCH PCB's yourself, new technique, no ch( 
cals, easy, cheap, full instructions, sharef- 
S1.00, SASE, NICKNAP, Suite 297 CN 1907, V 
NJ 07719. 



BARE bones Epram programmer, Plans/MS- 
DOS disk $15.00. Also parts/kits/assembted. 
SERGEANT, S09 W. San Antonio, San Marcos, 
TX 78666. 



CAULK l\ l)KS< KAMM.KK.S 

BEST BUYS BEST SERVICE 



BULLET PROOF TV TESTED 
WANT TO BUY: 
TO COM, SA SSBO.DPV72ia 
Mil at b* roMonabla price. 



SATELLITE TV 




FREE Catalog Dultra Wim.d 

Hum- Villon (402)33i-3£2a 800-835-2330 

Electronic*™ 2730 50.1 23rc Cl*126 Ctaihi. KE 68144 



WANTED 



INVENTIONS/ new products/ideas wanted: call 
TLCI lor free information/inventors newsletter. 1 
(600) 468-7200 24 hours/day - USAfCanada. 

INVENTORS: We submit ideas to industry. Find 
out what we can do for you. 1 {600) 288-lDEA. 

FORMAL blueprints from sketches and scratches 
— reasonable — confidential — mech/elec draft- 
ing. MICROCHIP THEATRE (718) 398-1163. 
Leave message. 



INVENTORS 



INVENTORS! Can you patent and profil from your 
idea? Call AMERICAN INVENTORS CORP. for 
free information. Serving inventors since 1975- 1 
(800) 338-5656. 



SATELLITE TV — Do it yourself — ma]or brands 
discounted, we'll beat everyone's price. DIS- 
COUNT LARRY (609) 596-0656. 

VIDEOC1PHER II, descrambling manual. Sche- 
matics, video, and audio. Explains DES, Eprom, 
CloneMaster, 3Musketeer, Pay-per-view (HBO, 
Cinemax, Showtime, Adult, etc) $16.95, $2.00 
postage. Schematics tor Videocypher Plus. 
$20.00. Schematics for Videocypher 032, $15.00. 
Collection of software lo copy and alter Eprom 
codes. $25,00. CABLETRON1CS, Box 30502R, 
Bethesda. MD 20824. 



CABLE TV 



FREE CATALOG 

GUARANTEED BEST PRICES • IMMEDIATE SHIPPING 

,M.K. ELECTRONICS,^ 

■JibTJl 03D2 Pints Blvd. Suite 276 

r^^H Pen broke Pints. Ft 33024 



PAIf TV AND SATELLITE 0ESCRAM8LING 

SIIIIIS 1992 EDI IIOJJ ALL MEW 



1992 Edition updslH laten Picuils. Tum-ons. Bypasses, fl-jllcts. Bags. Blade- 
gipturs. VCII Pits and BM)C Fun. Only t1S 95. VCII Wi?fjrrt Haetaii's pie 
inelmHntPlire TellsOl 515 91 Pjnr TV ing SalellrB Oeserjmbling Vol 1 (Ba- 
ses). 1989. 1991 f Hums i re all sMieitm. %H 95 ran MDS [Handbook S9 as 
Satellite Systems unHf %m SI 2 95 |S!), Any 3S39.95 « 5/S49.95. Scram- 
otaig Nevfi Monthly writ k«p you up to dale on Plus biiiks. S2J.95tyr. special. 
Everything yye nave including video. £10.95. Now Catalog SI. 



Scram tiring News, 1552 Heriet Ave., 
B u II :i l n tJY 1 421 6. Voice/Fax ( 71 6) 374 2Q88 

CODS ARE 0* fttrDii 




Cable TV 



1 *TH LU 1 1 T*^ 



> Hie Most Complete Line of Deicromblers 

> Friendly, professional service' 

>FREE Catalog 



ISEBHcpi 




1-800-228-740 



Go to tht So one 

NU-TEK ELECTRONICS 

3250 Hatch RD 
Ctdtv Parte TEXAS 78*1 3 



BUSINESS OPPORTUNITIES 

YOUR own radio station! Licensed/unlicensed 
AM, FM, TV. cable. Information $1.00. BRQAD- 
CASTING, Box 130-F10. Paradise, CA 95967. 

LET the government finance your small business. 
Grant&iloans to $500,000. Free recorded mes- 
sage: (707) 449-B6O0. (KS1). 



Is Bad Service Driving You Nuts? 






So don't crack up. Call MCM 
Electronics, toll free, at 

1-800-543-4330 

or fax 1-513-434-6959. 

We'll send you our free catalog. 

And show you how sane excellent service can be 



Business gets crazy enough without 
your electronic parts supplier driving 
you up the wall. That's why MCM 
Electronics dedicates itself to 
customer service, Weil answer and 
service your calls in just thirty 
seconds. We'll also answer your 
questions and give you advice. 
Whatever you need. Then we'll use 
our computerized order entry and 
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your order to you within 24 hours. Of 
course, you get more than quality 
service. You get quality parts and 
components; more than 17,000 of 
them, all available in our huge 
distribution center. 



^icn3 



MCM ELECTRON 

B5D CONGRESS PARK DR. 
CENTEIWILLE. DH 4545B-4072 
A PREMIER Company 




cs h***^ 



Source No. RE-79 



CIRCLE 8? ON FREE INFORMATION CARD 



1-800-8314242 Your Resource ft 



Test/ Measurement and Prototype Equipment 



Jameco Solderless Breadboards 




Jimcco't long- biting breadboard*, feature scr«n-princ«t color coorijinjitt and aje suitable for many kinds 
of proioiyping and circuit design. Large? models feature a heivy-dury aluminum backing wiih voltage and 
grounding poll*. 



P.rt No. 


Product No. 


Dim. I." I W" 


Co nun Points 


Binding Posts 


Price 


20600 


JE21 


3.25 i2.125 


400 





$4.95 


20722 


JE23 


6.50 x 2.125 


830 





6.95 


20757 


JE24 


6.50 x 3.125 


1,360 


2 


12,95 


20773 


JE25 


6.500 1 4.25 


1.660 


3 


17.95 


20790 


JE26 


6.875 * 5.75 


2,390 


4 


24,95 


20811 


JE27 


7.250x7.50 


3,220 


4 


32,95 



GoldStar 20MHx Dual Trace Oscilloscope 



The perfect unii Tor today's testing and measurement 
needs! Features include a G" CRT display, and bandwidth 
from DC to 20 MHz. The GoldStar oscilloscope comes 
with [wo 40MHr probes, two fuses, power cord, operation 
manual, schematics and block and wiring diagram. Its 
lightweight and portable with a two-year warranty. 

PjILNa, Product No. Description frfe 

18551 GS7020 Oscilloscope $399.95 




Additional GoldStar 
Oscilloscopes 



Part Product 

Ha, Hit, 



Description 



rrict 



66051 



GS904RD 40Mhz2 
channel 



66077 GS8100 



oscilloscope ...$799.95 

I00Mhi3 

channel 

oscilloscope ...1349.95 



Call for additional Goldstar 
test equipment 



JAMECO 8 

COHPUTEH PtTODUCTS 

24 Hour Toil-Free Order Hotline 

1*800* 831* 4242 



<£$£> 



Please refer to 

Mail Key 002 

when 

ordering 



Notional and Intel 




41224 400026 



41259 
41208 



400039 
400015 



Fin No. Product No. Description Price 

National General 
Purpose linear 
Devices Daiabook $19.95 
National Logic 

Daiabook 19.95 

National Data 
Acquisition 
Linear Devices 

Daiabook. 11,95 

National Special 
Purpose Linear 
Devices Databook...l 1.95 
National LS/S/TTL 

Databook 1 4.95 

Intel Memory 

Daiabook.. ..'. 24.95 

Intel Embedded 
Controller Processors 
Daiabook. 24.95 



41304 400104 



41275 
39280 
39870 



400044 
230843 
270645 




Metex Digital Multimeters 

■ Handheld, high accuracy * Measures ADDC voltage, AC/DC current, 
resistance, diodes, continuity, and transistor current gain {except M390Q) ■ 

1 Manual ranging w/ovcrloid protection 

• Comes with probes, batteries, case and manual 

M3650 Ic M4650 only. 

■ Also measures frequency and capacitance 

rul No, Product No, Description Price 

27115 M3SO0 3.5 digit multimeter ...$39.95 

27078 M3610 3.5 digit multimeter 59.95 

27140 M39O0 3.5 digit multimeter ^^Ttt ft* 

27086 M3650 35 digit multimeter V j4 "°* flot"* 1 

w/frequeney \ Qrd** „..&* 

& capacitance ,74.95 Hj] -rssjtS J 

27158 M4650 4.5 digit wl \\ # ^ .^sS* 8 ****' 

frequency & capacitance \^s^^^^^ 

&datahordswiich.„„„99.95 ^-e*~ 



IC Tost Clip Series 




* Test dips are designed for temporary connections to 
components 

* Heavy-duty spring loaded hinge provides positive cc 
Part No. P roduct No, Description 



22103 JTC16 

22120 JTC20 

22146 JTC24 

22162 JTC28 

22189 JTC40 



16'pln 

(for S, 14 o! 16-pin Kj).. 

20-pin 

(fot 18 & 20-pin 1Q) 

24-pin.. - 

28-pin. 

40-pin 



EPROMs - for your programming 

Plus- No, Product No. Prici Pin No, Product No. Price Pin No. Product Ni 



33566 TMS2516„„..$4.25 40248 

33603 TMS2564 5,95 39829 

33611 TMS27I6 5.95 39845 

37647 1702A 3.95 39853 

39909 2708 4,95 39992 

40002 2716 3,95 39925 

40011 2716-1 „ 4.25 34933 

39706 27C16 4.25 39950 

40096 2732 4,95 39968 

40109 2732A-20 .,4,49 39984 

40125 2732A-25 3,49 39677 

40133 2732A-45 .2.95 39685 

39765 27C32 .4,95 40070 

40192 2764-20 „ 3,95 40037 

40205 2764-25 3.75 40045 

4O230 2764A-20 3.75 40061 

A.R.T. EPROM 



2764A-25 „$3.49 65904 

27C64-15 .3,95 39714 

27C64-25 .3.49 39722 

27C64-45 2.95 39731 

2712SOTP J.49 40184 

27128-20 ...,7,95 40150 

27128-25. 7.75 40168 

27128A-15 .4,95 39773 

27I28A-20....„.4,75 39781 



27128A-25 
27C128-15 
27CI28-25 
272560TP 
27256-15..., 
27256-20.,, 
27256-25.., 



3,75 39790 

5.75 39802 

,....7.95 39651 

.....4.19 65699 

5.49 65681 

, 5.29 43692 

..,.4.89 



27C256-I2 
27C256-I5 
27C256-20 
27C256-25 
275120TP 
27512-20., 
27512-25 .. 
27C512-12 
27C5I2-15 
27C5 12-20 
27C5I2-25 
27C0I0-I5 
27CG20-15 
27C020-20 
68766-35 .. 




Additional daittbsoki gaiikUt! 



' Programs all current EPROMs in the 27 1 6 to 
275! 2 range plus i he X2864 EEPROM 

• RS232pon 

• Snftware included 

Pin No. Product No. Description Price 

16686 EPI> Prof,rammer.„.$t99.95 



UVP EPROM Era 




■ Erases ill STROM's 

• DE4 erases 8 chips every 21 minutes 

■ DEI erases I chip every 7 minutes 
PmNo. Product No. Description 



15712 DE4 
66042 DEI 



Eraser,,, 

Portable Eraser. 



• Partial Listing • Over 4000 Electronic and Compu 
Components in Stock! • CaUfbr quantity discounts 



CIRCLE 114 ON FREE INFORMATION CARD 



Value. Only a Phone Call Away. 



Computer Upgrade Products and Electronic Components 



Upgrade your existing computer system! Jameco will help you upgrade easily and economically. 
101 -Key Enhanced Keyboard Jameco 803 86SX Motherboard 




This keyboard feature! 12 function keys, separate 

cursor and numeric keys, 

■ IBM PQXT/AT and compatible computer! 

• Automatically switches between XT or AT 

• LED Indicator! for Num. Cips.and Scroll lock keys. 



Part No, Product No. Qejcripiign 



Price 




67432 



K101 



Keyboard $49.95 



Toshiba 1.44MB 3.5" Internal 
Floppy Disk Drive 



• IBM POXT/AT and compatibles 

• Compatible with DOS versions 3.3 or higher 

• Indudes all necessary installation hardware 

• 1 ,44MB formatted high density mode 

• 720KB formatted low density mode 

• Site: 1"H 1 4"Ws 5,9" D (actual drive size) 

• One-year manufacturer's warranty 

Part No. Product No. Tsnrriprinn 

40774 




Pri" 



JE1030: 

- Output: *5V £ L5A, -5V v? 0.5A, 
.12V0 5.5A. -12V@>0.5A 

• 1 50 watts output power 

• Switchable between 1 10/22OV 

• Built-in fan 

• Siie:9.5"Li5.5" , »'i4.625 , 'H 

• One-year warranty 
■ CSA approved 



53882 JB61SSN 

IBM Compatible P owe r Supplies 

JE1036: 

• Output: +5V(?20A.-5V<» 
0.5A,+ 12Vv? 8A. -12V v?0.5A 

• 200 watts output power 

• Switchable between 1 10/220V 
' Built-in fan 

• Size: 6.5" L i 5.88"W * 6"H 

• One-year warranty 
■ CSA approved 



' ]6M Hi processing speed 

■ Baby motherboard (!.5'il3"( 

* Zero or one wait state operation 

* Supports up to 16MB of RAM 

* Intel 80387SX/compatible math coprocessor socket 

■ AMI BIOS 

* Sis; 16-bit and two 8-bit expansion bus slots 

■ One-year warranty 
Pjit No. Prndno Noj JWrijmmi { 



Motherboard.. .$20 






356KU Disk Drive $99.95 

Many more upgrade products available! 



Pm No. Product No. Description 



JEria 



1*465 
19545 



JE1030 
JE1036 



150 watt PC/XT power supply $69.95 

200 watt AT power supply...........*.......,$89.95 



JJ-.10.-40 

Additional 

power supplies 

available! 



Integrated Circuits* 

Pan No. Product No. t-<> 10+ 

48979 7400 $.29 $.19 

49015 7402 29 .19 

49040 7404 29 .19 

49091 7406 35 .25 

49120 7407 35 .25 

49146 7408 35 .25 

491S9 7410 29 .19 

49728 7417 35 .25 

50008 7420 29 .19 

50235 7432 35 .25 

50420 7447 89 .79 

50551 7474 39 .29 

50593 7476 45 .35 

50665 7486 45 .35 

50681 7489 ......2.95 2.75 

50690 7490 59 .49 

49322 74121 .49 .39 

49912 74192 .79 .69 

49939 74193 .79 .69 

linear ICs* 

Put No. Product No. fcS 

33241 TL0S2CP $.59 

23579 LM3 17T 59 

23683 LM324N 35 

23771 LM336Z 1.09 

23851 LM339N 45 

27422 NE555V. 29 

24328 LM556N .49 

24467 LM723CN 49 

24539 LM741CN 29 

23 1 31 LM 1458N. 39 

23157 LM1488N 45 

23181 LM1489N .45 

34278 ULN20O3A 69 

24230 LM3914N 2.49 

27385 NE5532 1.19 

51262 7805T .45 

51334 7812T .45 

" Name brand ICs in stock 



IC 

Psut Product 
Ma, Ma, 



51570 8LP 

37161 14LP 

37372 16LP 

39335 24 LP 

40301 28LP 

41110 ■:■:.■■. I ' 



Pin 



Sockets 

Dmririli 



Prio 



Product 

Jia. 



8 -pin low profile ....$.10 
14-pin low profile ... .11 
16-pin low profile ... .12 
24-pin low profile ... .19 
28'pin low profile ... .22 
40-pin low profile ... .28 



JEiisj. 



Description 



15114 DB25P Male, 25-pin $.65 

15157 DB25S Female, 25-pin .75 

15085 DB25H Hood 39 



15106 DB25MH Metal Hood 1.35 

Miscellaneous 

Components* 

Transistors And Diode s 

Part Product 

Ma. fck, Ik 



rlptio 



Prjce 



28628 
28644 
35991 
38236 
36126 
38359 
36290 
38421 
36038 
38308 



PN2222 TO-92 owe $.12 

PN2907 TO-92 cut ..„.. .12 

1 N 4004 D041 cut 10 

2N2222A TO-18 cue 25 

1N473S DCM1 case 25 

TO-92 oat 12 

DO-35 cast 15 

TO-92 cut 15 

DO-35 cast 07 

TO-3 cue 69 



2N3904 

1N751 

2N4401 

1N4148 

2N3055 



Switches 

Part Product 

No. No. Deacripliog 



(V,.- 



21936 JMT123 SPOT, 

on-on (toggle) ....$1.15 
38842 206-8 SPST, 16- pin 

(DIP) 1.09 

26622 MS102 SPST, momentary 

(push-burton) 39 

'Additions.! components available 



Put No. Product No. 



Fung ion 



41398 
42251 
41523 
41718 
41769 



41256-120 

511000P-SO 

41256A9B-80 

421OO0ASA-8O 

42IOO0A9B-8O 



25GK DIP 
1MB DIP 
256KSIMM 
1MBSIPP 
1MB SIMM 



r .''Hi- -. 

80ns.,.. 

30ns... 
80ns .... 
80ns... 



LEDs 

Put No. Product No. PnrriirTinn Cjoss 

34761 XC556G TI 514. (Green) $.16 

34796 XC556R Tl 3/4. (Red) 12 

34825 XC556Y Tl 3/4. (Yellow) .16 



Call or write for your 
1993 .Annual Catalog: 
1-800-637-8471 




M<«£.* 



'■J* 



24-Hour Toll-Free Order Hotline: 

1.800*831*4242 

JAMECO 

COMPUTER PRODUCTS 

1355 Shoreway Road 
Belmont, CA 94002 



Men 
Mail 



r-pf-j $30.00 Minimum Order 
FAX: 1-800-237-6948 (Dom«ie) 

FAX; 415'592-2503 ([ruemKiand) 

Jameco ServiceUne™ : 

1 >800'83 1 -8020 (Csmpuifr Repair) 

Technical Support: 1.800-83 1-0 
BBS Support: 41 5-637-9025 



For International Salts, Customer Service, Credit Department and all 
inquiries: Call 4l5'592'8Q97 between 7AM-5PM P.S.T. 



CA. Residents please add applicable uls tax. 

^^^^__ 1 *E [ Shipping, handling 

ELJiiin lUOSl arid! i-osurtiricc are 
fS^ZJ ^2 Edition,!. 



Terms; Prices subject to change without i 

Items subject to availability and prior tali: 
Complete liic of lefms/wjrranrtcj is avail; 

upon request. 



€ I992Jamea 10(92 All indemarb ait regmeied xraderaaiLi of [heir respective camps 



CIRCLE 114 ON FREE SNFQRHATlON CARD 



CABLETRONICS 



CONVERTERS 



1-4Unt1s S Units 10 Units 



PANASONIC TZP 145 
STARGATE 2000 
HAMLIN MCC 3000 



$88.00 
$79.00 
$25.00 



$75.00 $70.00 
$69.00 $65.00 
$19.00 $15.00 



ADD-ON DECODERS 



SB-3(NEW) $50.00 $45.00 

*SB-3 FACTORY $45.00 $39.00 

SA-3 $56.00 $50.00 

DTB-3 $65.00 $55.00 

KNI2A-2 or 3 $49.00 $45.00 

*HAMILIN MLD 1200-3 $49.00 $40.00 

*ZENITH SSAVI $165.00 $149.00 

SA-DF $159.00 $139.00 



JERROLD DPV7 
JERROLD DPBB 
SA8580 COMBO 
MERROLD DRX-3-DIC 
JERROLD DR2-3-DIC 
*OAK M35B 
HAMLIN SPC 4000 3M 
ADO *1 0.00 FOR VARISYHCH 



COMBOS 

$299.00 
$319.00 
$299.00 
$165.00 
$175.00 
$45.00 
$50.00 



$149.00 
$259.00 
$225.00 
$105.00 
$115.00 
$35.00 
$44.00 



$43.00 
$35.00 
$45.00 
$50.00 
$40.00 
$35.00 
$125.00 
$12500 



$239.00 
$249.00 
$215.00 
$89.00 
$99.00 
$30.00 
$44.00 



♦Refurbished as New 



QTY 



ITEM 



OUTPUT 

CHANNEL 



California Penal Code *593-D Forbids us from 
shipping any cable detcrambling unit to 
anyone residing In the state of California. 
Prices subject to change without notice. 



Please Print 

Name 



PRICE 
EACH 



SUB TOTAL 



Shipping Add 
5.oo Per unit 



SOD/QwmCaid 
Add 5% 



TOTAL 



TOTAL 
PRICE 



Addreas_ 
State 



_Clty_ 



_Zp_ 



D Cashier's Check Q Money order 
Dvisa Dmc CC# 



-Tel:< L 



□ COD 



_Exp. Date_ 



DECLARATION OF AUTHORIZED USE- 1, Hie undersigned, do hereby declare 
under penalty of perjury that all products purchased, now and In the future, 
will only be used on TV systems with all applicable federal and state laws. 
FEDERAL AND VARIOUS STATE LAWS PROVIDE FOR SUBSTANTIAL 
CRIMINAL AND CIVIL PENALTIES FOR UNAUTHORIZED USE. 



Date 



Slgned_ 



Cabletronics 

9800 D Topanga Canyon Blvd. , Suite 323, 
Chatsworth, CA 91311 

For Free Catalog, or to place an order call 

{800) 433-2011 • FAX (818) 709-7565 



FREE CATALOG 

1-800-648-7938 

JERROLD HAMLIN OAK 

CABLE TV 



■ WHlfiVj = \m 



• Special Dealer Prices! 

• Compare our Low Retail Prices! 

• Guaranteed Prices & Warranties! 

• Orders Shipped immediately! 

REPUBLIC CABLE PRODUCTS, II 

4080 Paradise Rd. #15, DeptREios 
Las Vegas, nv 89109 
For all other information (702) 362 ■&' 



EASY work! Excellent pay! Assemble prod 
home. Call loll tree 1 (600) 467-5566 Ext. 

HOME assembly work available! GuarE 
easy money! Free details! HOMEWORK-! 
520. Danville. NH 03819. 

MONEYMAKERS! Easy! One man CRT r< 
ing machinery. $6,900.00 rebuill. $1 5,900.0 
CRT, 1909 Louise. Crystalake, IL 60014. 
477-6655. FAX (815) 477-7013. 

MAKE $75,000.00 to $250,000.00 yearly o 
fixing IBM color monitors. No investmenl 
doing it from your home (a telephone req 
Information, USA. Canada $2.00 cash fc 
chure, other countries S10.00 US lunds. 
DALL DISPLAY, Box 2168-R, Van Nuy 
91404 USA. FAX (818) 990-7803. 



FREE CATALO 



• CABLE T.V. BOXES - ALL TYP 

• LOW PRICES - DEALER PRIC 



Ace Products 

1-800-234-0726 



CONTINGENCY patent licensing. No lee 
time. Three decades experience:1aw, techi 
negotiations. PROPAT INTERNATIONAL 
PORATION, 441 Summer Street, Stamfo 
06901(203)325-3344. 

LE A R Ng ol d, silver, platinum scrap recycl i n 
ness. (Free) information. Write: RECYC 
Box 11216PE, Reno, NV 89510-1216 

ELECTRONICS dealers: Expand your f 
line. Make SSS! Become an AMERICAN 
TRONICS dealer! Profit opportunities sinci 
Call Scott Pruett, 1 (800) 872-1373. 

$ Millions on inventions secrets. Send S 
and $5.00 payable Carl Humphreys, to ll 
TION MILLIONS, 3012 Rax, El Paso, TX 7 




***** STARRING ****- 

JKRROLO, HAMLIN. OA 

AMD OTHER FAMOUS MANUFACTURERS 

• FINEST WARRANTO PROGRAM AVAIL^aL£ 

■ LOWEST RETAIL (WHOLESALE PRICES IN U 

■ ORDERS SHIPPED FROM STOCK WITHIN 24 H 

• ALL MAJOR CREDIT CARDS ACCEPTED 

FOR ALL INFORMATION 

1.S00.345-B927 . 



PACIFIC CABLE CO.. INC. 

7325'j Reseda Blvd.. Dept. 21 

Reseda, CA 31335 



BEST BY MAIL 

R>m: Write National, Box 5, Strtwtt, FL 34230 



BUY IT WHOLESALE 



aj 



FULL- OR PART-TIME JOB/BUSINESS: 



BUV 30% ' 80% Below Wholesale: Apparel • Electronics 
W.B6 - BOULOS. Son 55027. Sherman Oaks, CA 91413. 

MOHEVMAKINQ OPPORTUNITIES 

J1BO0.00 A WEEK AT Home. For Free Information Send A 
Stamped Envelope To: American Dream. PO Box 1533-1. 

North Wales. PA 19454 

NEED SECOND INCOME??? Details $9.98: Thomas, Box 
16801. Jacksonville, FL 32245-6601. 

ASTRO LOQY 

CHINESE HOROSCOPE 1 900-448-0611 $2.00 Per Minute 

18+ LH Services. Ft. Lauderdale, FL 33308 (305)564-3022. 



EDUCATION & INSTRUCTION 

F.C.C. Commercial General Radiotelephone li- 
cense. Electronics home study. Fast, inexpen- 
sive! -Free" details. COMMAND, D-176, Box 
2824, San Francisco, CA 94126. 

ELECTRONIC engineering. S volumes com- 
plete. $109.95. No prior knowledge required. Free 
brochure. BANNER TECHNICAL BOOKS, 1203 
Grant Avenue, Rockford, IL 61103. 

PATENT it yourself. Eliminate huge fees. Com- 
plete practical instructions $9.95: PATENT 
GUIDE, PO Box 654, Gurnee. IL 60031. 

LEARN electronics and digital basics. Pro- 
grammed courses. $17.00 each, bolh $29.00. 
Satisfaction guaranteed. TEK SOURCES, 60S0 
NW 68th St., Parkland, FL 33067, 

SAVE $ importing radios, electronics... directly 
from manufacturers. For business' hobby. Guar- 
anteed easy! $2.00. MINTER ENTERPRISES, 
Box 8002-R, Westchester, OH 45069. 



Learn VCR repair! 
i 

i 
i 
i 



Professional -level home 
study program. Master jf^ 
easy-to- learn, high-profit 1 
repairs without investing I 
in costly high-tech instru- 
ments. Send or call today. 

Free career kit: 
800-223-4542 

Name 




Address - 



. State _ 



-Zip- 



| City 

I The School of VCR Repair, Dept. VL342 
2245 Perimeter Park. Atlanta, GA 30341 

■■i ^m ^m ^m ^m ^m ^m ^m ^m «■ ■« ^m v ■ 



MUSICIANS, build a high quality digital delay, 
$10,00, very high quality duophonic synthesizer 
— S10.0O. Kits also available. GEBHARDT, Box 
754. Anaconda. MT 59711. (406) 563-7506. 

BUILDING A Robot: A Straightforward Approach. 
152 pages fully illustrated. Instructions how you 
can easily construct a robot. Check or money 
order. $19.95 plus $3.00 shipping. HUMANFORM 
ROBOTICS, PO Box 158486, Nashville, TN 
37215. 

BUY BONDS 



MC / COD / VISA 
NO FLORIDA SALES 



CABLE TV DESCRAMBLERS 



WORLDWIDE CABLE 

• BASE BAND * PIONEER 

• T0C0M ■ ZENITH 

• SCIENTFE ATLANTA • DAK 

■ JERR0LD • HAMLIN 

1 800-772-3233 

1291 A PDWERUNE H0A0, SUITE 109 
P0MPAN0 BEACH. FL 33069 



CABLE TV DESCRAMBLER 

* CONVERTERS ^ 

and ACCESSORIES. 




PANASONIC, JERROLD, OA 
PIONEER, SCIENTIFIC ATLAN 

AND MORE. LOWEST PRICES. FREE CATALC 
CABLE READY 
COMPANY 



(800)234-100 



fr 




$19fach 



Technician 



Turntable to spMd 
repair of VCFls.TVs 
and mora, Lets 
technician easily 
turn unit for 

convenient repair. 20' di 
While color. Mel weigh! 

#RH-360-425 



Super Horn Tweeter 



The original 
piezo tweeler 
manufactured 
by Motorola. 
Sens "ivilv 94 UB 
2,KiV/1M. 25-30 
volts (approxi- 
mately 50 walls) 
power handling 
capability. 
Produces crisp, 
clean highs. 
Frequency response; 4 KHz-27 KHz. 
Dimensions: 3-3/0* x 3-3/8' x 2-5/8". 



Piezo Super Tweeter 




This extremely 

small tweeler 

incorporates all the 

advantages or piezo 

tweeters inlo a 

small package lhat 

can be mounted. 

almost anywhere. Frequeni 

5K-20KHZ SPL: 97dB1W, 

handling: BO watts RMS, when used 

with a 4.7 microtared capacitor. Sold in 

pairs. Net weight: 1/2 16. 



™ 



.cy response: 
V/1M. Power 



#RH-265-267 



3 - hole. MotoraSa ttKSNtOOSA 

#RH-270-Q10 SS 30 $4 M $3 M #RH-100-151 

(1-9) (10-79) (80-up) 

8" In-Wall Subwoofer 

8' paper cone subwooler with polymer 
resin coating. Dual voice coils with 8 ohm 
impedance per coil. Ported plate speaker 
with integral crossover. Frequency 
response: 30-500 Hz. 50 waits RMS, 100 
watts maximum power handling capability. 
Sensitivity: 90dBlW/lM. Dimensions: 
1 0-5/8" fW) 1 4-5/8" (L) x 3" (Oj. 
Hole dimensions: 9 (VV) x 13 
Net weight: 8 lbs. 

Sug List 

$192 K 



$24°° $22*° 

(1-3) (4-up) 

12 Ga. Speaker Wire 

Extra large gauge 
speaker wire for use 
with very high power 
stereo systems and for 
use in extremely long ■ 
cable runs. Over 250 
slrands of 36 ga. wire- 
Extra Ihick. clear PVC 
insulation. Please 
order in multiplies 
of 5 teat 



BBC 12" Dual Voice Coil 
Subwoofer 

Super quality Kalian 
made cast frame dual ,* 

voice coil subwoofer. / j 
Paper cone wilh loam / 
surround. 2" dual 
voice coil. fs= 45 Hz. 1 
Frequency response: 
45^4KHz. Sensitivity: 
96.63 1W/1M. VAS= 
3.73 cu ft., QTS^.338. 
BBC *SW32t/FB. Net 
weight: 9 lbs. 

#RH-294-130 



39* 

(per Foe!) 



V) X 13' (L). 



#RH-300-430 



/I r Parts 

'express 



S85 50 

(1-3) 



$79" 

(4-up) 







VCR Parts Assortment 



Convenient 

assortment of clips. 
washers, springs, and 
screws. 1 pieces 
each of 4 sizes of "E* 
clips, 10 pieces of 
2 sizes of retaining 
rings, 10 pieces or 14 
sizes of washers, 2 
each of 8 sizes of 



. • - 



S139 

(1-3) 



$128* 

(4-up) 



tension and compression springs and 
24 assorted screws. Total of 246 pieces. 

#RH-43tKJ15 



8 Ga. In-Li 



$6» $5* 

(1-3) (4-up) 

Suction Cup Mount 
Fuse Holder Cellular Antenna 




The ideal antenna tor 
portable phones. Suction 

cup grip mounts on inside 

of car. Never have your car 

vandalized again. Antenna 

comes wilh 9 feet ol RG-5S 

with TNC connector. 3 d8 

pain. Made in the U.S.A. 

9' overall height. 



#RH-265-200 



43s ^ 



^ 



I* 30 day money back guarantee ■ $20,00 minimum order * We accept 
Mastercard, visa , Discover and C. Q. D . orders. • 24 hour shipping 
i + Shipping charge = UPS chart rate + $1 .00 ($3,50 minimum cha rge) 
Idft F Fir<st St Dflvlnn flhirl dRdn? ^Hour38:30arn-7:OOpoiEST,Monday-Friday'9:OOam-5:OOpm 

Loca 1 : 1-513-22 2-0 173 on orders exceeding 5 lbs. < Foreign deslinalion customs rs please 

FAX" 513-222-4644 send ^ l00 u '^ ^ u " ds 'w*»tBlofl poslage ■ 



Screw together Bakolile fuse holder with 8 
ga. wire. For use with AGU type fuses Or 
regular AGO fuses when spring spacer is 

used. 50 amp max al 12 volts 

#RH-070-a00 $3=° $2 75 

(1-9) (10-up) 

High Voltage Cap Kit 

This 85 piece kit contains a 

selection of 250, 350, and 450 voll 

electrolytic capacitors. 5 pieces 

each of1. 2.2, 3.3, 4.7. 6.6, 10. 22ut 

and 2 pieces each ol 33. and 47uf . 

250V radial caps. 5 pieces each of 

1, 2.2,3.3, 4.7, 10uf and 2 pieces 

each ol 22, 33gf, 350V radial caps. 

S pieces each of 1 , 2.2. 4.7uf and 2 

pieces of lOuf. 450V radial caps. Over $52.00 wholesale 

cost if purchased individually Net weight: 1 lb. 

#RH-020-950 $49^ 

FREE CATALOG 
CALL TOLL FREE 
1-800-338-0531 



$14r? ach 




CIRCLE 56 ON FREE INFORMATION CARD 






I 



5 

o 



g 

4 



104 





Remember Ihose Martian 
Space Ships in HG Wells 
Wic of the Worlds?^ 

MYSTERY 

Levitating Device 

Objects floal on air and move lo the 
touch. Defies gravity! Amazing gift, 
conversation piece, magic kick or 
great scienliftc project 
ANT1K Easy-Assy Kib'Planajl 9,50 

3 MILE 

FM Wireless 
Microphone! 

Ciysial dear, ultra-sensitive pickup 
transmits voices, sounds lo any FM 
radio. For security, monitoring 
children, invalids. Be the local DJI 

HVP1 Plans $7.00 

MVPIKKiUPIans $39.50 

3 MILE 

Telephone 
Transmitter! 

Automatically transmits 2 sides ol 
phone conversation to any FM radio. 
Tunable, easy-assembly PC board. 
Operates only when phone is In use. 

VWPM7 Plans $7,00 

VWPMK7 KitfPlans $39.50 




TV & FM Joker/Jammer 

Pockel size device lets you ramolely 
disrupt TV or radio reception. Great 
gag! Discretion required. Easy-build 
electronic kit. EJK1KM $1 9.50 

100,000 V -20' Range 
Intimidation Device! 

Electronic module, may be enclosed 
tor handheld, portable, or fixed uses. 
ITM2 Plans (creditable to kit) S10.00 
ITM2K Kit 4 Plans $49,50 

READY-TO-USE, AUTOMATIC 

Sy h sTem Ree0rdin9 ®® 

Complete with extended play tape 
recorder & line interlace switch. 
Automatically records both sides of 
conversation. Check Local taws on 
Proper Usel Ready-to-Use System. 
TAP20X System .... $149.50 



INFORMATION UNLIMITED 

Dept RE-4 Box 716, Amherst NH 03031 
Phone 603-673-4730 FAX 603-672-5406 
MC, VISA, COD, Check Accepted, ADD $5 S&H. 



\. Order by 



Laser Pen 

Pen sized laser, great for movies, 
drive- ins, pointer. Ready to use, with 
s. LAPN1 User Pen , $149.50 



Pocket Laser Kit 

3mw or 5mw kits, with solid slate 
670nm diode. Caution, Class Ilia item. 
VRL3KM 3mw Laser Kit . . . $99.50 
VR L5KM 5mw Laser K i l . . $119 .50 

MORE Laser Kits! 

LAS1KM 1mw Laser, 632nm, HeNe 

Easy to Build Kit $59.50 

LA S4KM 3m w Version, Kit $99 .50 

LAT05 Low Cost HeNe Laser Tube! 
.5mw Tube & Plans . . only $24.50 

Other parts available separately. 
Great Low Budg et Science Project! 



Shocker Force Field 
^Vehicle Electrifier 




Mall, or by 
24 Hr Order Phone: 

600-221-1705 



Make hand shock balls, shock wands 
electrify objects, charge capacilors. 
Great pay back lor those wise guys! 
SHK1KM Easy-Assembly Kit$24.50 



CATALOG! 



with many more items! 

FREE with order, or send $1 F&H 




|#EX192 



All major brands carried 
*JERROLD, *TOCOM, *ZENTTH 
♦GENERAL INSTRUMENTS 
♦SCIENTIFIC ATLANTA, *OAK 
♦HAMLIN, *EAGLE, *PIONEER 
7th Year in business. Thank You 
Member of Omaha Chamber of Commerce 
1 Year warranty on new equipment 
30 Day money back guarantee 
Orders shipped from stock within 24 hours 

CALL TODAY FOR A FREE CATALOG 

1-800-624-1150 



M H LB c.o.d. 

| MiDi?EJiEGTR©NieS^ 

% ^ 875 SO. 72nd St 



Cable TV 
Descrambler Kits 



Universal Kit $55.00 

includes ail parts and PC Board. Not included 

is the ac adaptor or enclosure 

Tri-Mode Kit $39.00 

includes all parts. PC Board ana AC Adaptor. Mot 
Included is the enclosure. 

SB-3 Kit $29.00 

includes all parts. PC Board and AC Adaptor. Not 
mcluoed is the enclosure 

Universal Tutorial,.... $9.95 

includes an in depth study of trie tecncncicgy u»d 

and has troubleshooting hints. 

Tri-Mode Tutorial S9.95 

Includes a gate by gate study of the circuit and has 

troubleshooting hints. 

Snooper Stopper $39.00 

Protect yourself trom descrambler detection and 
stop the 'bullet'. 



Call Toll Free 

1-800-258-1134 

C.O.D. 

M & G Electronics, Inc. 
301 Westminister Street 
Providence, Rl. 02903 




CIRCLE 53 ON FREE INFORMATION CARD 



CIRCLE 197 ON FREE INFORMATION CARO 



QUALITY PARTS - DISCOUNT PRICES « FAST SHIPPING 



(mmMMmmm 



Small 

Neodymium 

Magnet 



O 



Smafl. powerful 
neodymium 
mag not. Irregular 
shape approx. 0.64 ■ X 0.7" 
X 0.1" thick. Strong (or its 
Size. CAT* MACS 
J 1.50 each 



Digital Voice Module 



Ming* DVM-10B. Digital recording module 
especially suited tor reproducing verbal messages. 
Ideal lor HAM contesting, memo recorder, verbal 
alarm system etc Requires a minimum of external 
wiring. Up to 8 different phrase channels. Built-in 200 mW audio amp. 1 Mega- 
bit of DRAM memory, for up to 32 seconds of recording. Condenser or dynamic 
mike Input. Board size: 3 3/4* X 2" X 1" high. Includes memory chips which re- 
quire installation. Microphone and other external components not included. 
CAT* DVM-108 (25.00 each 




A.C. Line Cord 



=^= 



6 ' Black 18/2 A.C. power cords. SPT-1 Insulation. Polarized plug. 
CAT* LCAC-7 2 for 1 1 .00 ■ 1 00 lor $45.00 ■ 1 000 for $400.00 



Car Lighter Coil Cord 



<jD_j3===5aMSarH%y^SA 



ELECTROL UMINESCENT 
Piezo Element L.E.D.'s BACKLIGHTS 




3 Wire 

Plezo Element. 

Taiyo Yuden Co. * 

C335BBKR4. 

Self-ear cited piezo 

electric diaphram 

1 .40" diameter x 0.021" thick. 

Resonant resistance: 400 ohms. 

5" color-coded leads, 

CAT#PE-12 $1.00 each 
1 lor $8.50 ■ 1 00 for $65.00 



Flash Units 




t»i 1 >J* 



NEW compact flash assemblies 
from a camera manufacturer. 
Operates on 3 Vdc . Meas u res 
2 1/2" X 1 1/4-. Ideal for use as 
a strobe, warning light or atten- 
tion getter. Includes a hook-up 
diagram. CAT* FSH-1 
$3.75 each ■ 10 lor $35.00 
100 for $325.00 



12 Volt 2 Amp 
Transformer 



Same as Mouser 
#41FG020. 
12 VCT. 2 Amp , 
power transformer. 
2" X 2.35" X 2.10". 2.90" mount- 
ing cenlers. Pigtail leads. 
CAT#TX-122A $5.00 each 




Surface mount 
LED chip. 

Clear when off. green when lit. 
Very thy - whole unit Is 0.1 15' 
X 0.055' X 0.06" thick. 1rrm 
(0.04") lens diameter. Gold- 
plated mounting surfaces for 
superior conductivity. 
CAT*SMLED-2 10 for $2.00 
100 for $18.00 
1000 for $140.00 

Standard JUMBO 

Diffused T 1 -3/4 size {5 mm) 



RED CAT* LED-1 
10for$1.S0'1001or$13.00 

GREEN CATKLED-2 

1 for $2.00 • 100 for $1 7,00 

YELLOW CAT*L£D-3 

10 tor $2.00 -100 lor $17.00 

REDUCED PRICES 
FLASHING LED 

W built in Hashing circuit 
5 vol! operation. T 1-3/4 
{5mmj 



RED 50c each 
CAT*LED-4 10 for $4.75 

GREEN 75t each 
CAT* LED-4G 10 lor $7.00 

YELLOW 75C each 
CAT* LED-4Y101or $7.00 

LED HOLDER 

Two piece holder. -_ 

3 S 



Automotive cigar lighter plug with replaceable 5 amp fuse. Quality. 

retractable coll cord extends to approximately 6 feet. Terminates with a 

5 ph DIN plug which can be cut-off. Ideal for battery charger or running 

\\2 Vok devices from car battery. CAT* CLP-18 $1.50 each • 10 lor $12.50 



D.C. Wall Transtormers (120 Vac INPUT) 



At last! A low cost electroluminescent 
glow strip and inverter. These brand- 
new units were designed to backlight 
small LCD TVs made by the Citizen 
Watch company. The inverter circuit 
changes 3 or 8 Vdc to approximately 
100 Vac, the voltage required to light the 
gkjwstrip. Luminescent surface area Is 
1JX 255". The si rip is a salmon color 
In Is off state, and glows white when 
energized. The circuit board is 2.2" X 1". 
Gow sr rip and circuitry can be removed 
easily Irom plastic housing. Ideal for 
special lighting effects. 

Citizen* 92TA operates on 3-6 Vdc 

CAT#BLU-92 $3.50 each 

LARGE QUANTITY A VAILABLE 

10 for $32.00 "100 for $275.00 



Monoral Equalizer 



4 Vdc 
6 Vdc 
8.3 Vdc 
9 Vdc 
12 Vdc 
12 Vdc 
12 Vdc 
12 Vdc 

14 Vdc 

15 Vdc 



70 ma. 
300 ma. 
10 ma. 
300 ma. 
100 ma. 
500 ma 
800 ma. 
1 Amp 
700 ma. 
400 ma. 



2.5 mm co-ax 
2.1 mm co-ax 
battery snap 
2.1 mm co-ax 
2.1 mm co-ax 
2.1 mm co-ax 
2.5 mm co-ax 
none 

1 .3 mm co-ax 
2,5 mm co-ax 



cenhw 

negative 

posKtve 

positive 
negalhre 
negalhre 
posllfve 

negative 
negalkre 



cm 

DCTX-470 

DCTX-632 

DCTX-8310 

DCTX-W2 

DCTX-1210 

DCTX-125 

DCTX-1281 

DCTX-121 

DC TX- 14 70 

DCTX-1S4C 



$2.00 
$2.76 
$1.50 
$3.00 
$2.50 
$4.50 
$5.25 
$6.50 
$5.25 
$4.50 



10 for 65c 




*%% »« .2Sf , ■" 10 WATT SWITCHING 

17 Vdc 210 ma. WALL __..„__ . .. 

TRANSFORMERS POWER SUPPLY 



New 17 Vdc, 

210 ma wall 

transformers. 

6 ft. cord. 

Unusual 

co-axial device on end of 

cord can be cut off and used 

lor another application. 

Large quantity available. 

CAT* DCTX-1731 $1.50 each 

100 lot $1.25 each 

1000 for $1.00 each 





Rechargeable Batteries (nickel-cadmium) 



1 



Five band graphic equalizer. Allow* use 
of one source for background rru s ic and 
mu dc -on -ho Id. Allows you to equalize 
and adjust the volume of one without 
changing the other, Useful In an/ appfl- 
catbn where equaJzatlon o( a monoral 
source Is cfosirabJe. RCA jack Inputs and 
outputs. Removable metal control cover 
to prevent lanpering. 67S"X5.75"X 
3.125" high, CATfECM 115.00 each 



10 AMP SOLID 
STATE RELAY 



(USED) 
10 amp 
solid state 
relays, removed 
from equipment and tested. 
Control voltage: 250 volts AC 
at 10 amps. Standard "hock- 
ey-puck" size: 2.27" X 1 ,72" X 
0.95" . UL and CSA listed. 
CAT#SSRLY-11U 
$8.25 each ■ 10 lor $80.00 



AA 



1.20 IBOmAh 
1.20 500 mAh 



NCB-AAA 

HCB-AA 



LCD Display ' 40 Character X 2 Line 



SO WATT 
Computer Products f XL40-8301 
Input: 115/230 Vac 
Output: -12Vdc©0.2A 
12 Vdc® 2,0 A 
5.1 Vdc #3.5 A 
Switching power supply. 
Regulated. 6.30" X 3.93* X 1 .9" high. 
CATCPS-51 $15.00 each 

TtWATT 

Computer Products # XL50-B601 
Input: 115/230 Vac 
Output: -12 Vac® 1.0 A 
12 Vdc 9 1.0 A 
5 Vdc @ 6.0 A 
Regulated switching power supply. 
7.76" X 4.25" X 1.78" high 

CAT* PS-76 $20.00 each 



12 VDC STEPPER MOTO! 



$1.50 
$2.00 



$13.50 
$18.50 



SokierT.be 1.20 500 mAh NCB-SAA $2.20 $20.00 
SubCw/ 

SoHe-Tabe 1.20 1200mAh NCB-SC $4.25 $40.00 

C 1.20 1200mAh NCB-C $4.25 $40.00 

C Heavy Duty 1.25 1800 mAh HDKCB-C $5.25 $42.50 

1.20 1200 mAh MCS-D $4.50 $42.50 

Duty 1.25 4000 mAh HDMCB-D $7.00 $65.00 




Optrex # DMC40218 or Hitachi f LM015L 

Built-in corttroier and drivers. 4 or Sort operation. 5 Vdc power. 

Display size: 6.05" X 0.7" Module size: 7.12* X 1.34". Character size: 

(5X7 dots) 3.2mm X 4.85 mm. Data sheets and Instructions available. 

CAT#LCD-3 $15.00 each 




Airpax* AS 37 12- Ml 

12 Vdc. 36 ohm coil. 15 degree/step. 

2.25" dim. X 0.95" thick. 

0.25" shaft X 0.6" long. 

CAT#SI*T-« $6,00 each 



ORDER TOLL FREE 1-800-826-5432 



Call Or Write 

For A 

free 64 Page 

Catalog 

Outside the U.S.A. 
send $2,00 postage. 



FAX (818) 781-2653 * INFORMATION (818) 904-0524 

Minimum Order $10.00' All Orders Can Be Charged To Visa, Mastercard Or Discovercard « 

Checks and Money Orders Accepted By Mail • California, Add Safes Tax • No C.O.D. * 

Shipping And Handling $3.50 for the 46 Continental United Stales - All Others Including Alaska, Hawaii, 

P. R. And Canada Must Pay Full Shipping • Quantities Limited * Prices Subject to change without notice. 



MAIL ORDERS TO: ALL ELECTRONICS CORP • P.O. BOX 567 • VAN NUYS, CA 91408 



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I 



s 

i 



106 



"CABLE BOXES" 

BELOW WHOLESALE 

GUARANTEED STOCK - COD'S 



DESCRAMBLERS - 



(QTY) 
NEW TBI 3 


(10) (20) 
70 55 


(40) 
CALL 


TB 2 or 3 
SA-3B 
OAK N-12 
SB 2 OR 3 


45 40 
45 40 
43 38 
43 38 


CALL 
CALL 
CALL 
CALL 


COMBINATION UNITS 



DRX-D1C 89 CALL 
SYL DIC 59 CALL 
PIONEER 295 275 CALL 

- CONVERTERS W/REMOTES - 

PANASONIC- 
TZPC145 65 60 CALL 

STARQUEST- 
E-Z550 65 60 CALL 

E-ZY550 75 65 CALL 

THEFT OF SERVICE IS * CHIME INSTALLED ANY DEVICE 
WrTHOLTT PERMISSION MAY SUBJECT YOU TO CIVIL OR 
CRIMINAL PENALTIES YOU MUST CHECK WITH YOUR 
LOCAL CABLE COMPANY AND PAY FOR ALL SERVICE YOU 
USE IT IS NOT THE INTENT OF LAKE SYLVAN TO DEFRAUD 
ANY TELEVISION OPERATOR AND WE WILL NOT ASSIST ANY 
COMPANY OR INDIVIDUAL IN DOING THE SAME 

LAKE SYLVAN SALES, INC. 

SORRY NO MINNESOTA SALES 



CALL FOR A CATALOG NOW!! 

800-800-4582 



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THE ELECTRONIC GOLDMINE 




OoUmm* fas ore d die 
QnHtey setottofB d irirjjG 
fcteJvailatte n 
*e worif We fm 

barjtn priced, componorti 
■nam caiairfl 1 



INFRARED DETECTOR 
KIT 

GttM lor iMlng and wf chai d 
nharttt CuEpJl 9V hat\rf ml r>3LKJod 

C6441 $5. B 



oOEP"; 



INEXPENSIVE CEIGER 
COUNTER KIT 

Gjtftj Ftayi 



PRECISION 
HIGH I 
MOTOR 

Groat lor Ffctw I.. . 

rtjre larn «>c 5:( 1 W . flUfi? 

Dpvtttlom 1CMjC upfciBVDC 

G2S45 1 ," H lOrfc." 




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*» hum any 1 jv trty h 
[ft*} EV1 u.i abM| mo: arq 1 

G2744 89« 



BURGLAR/FLUE 

ALARM KEYBOARD 

CONTROL PANEL 



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n ibhtb Thay «rt*«i 11 o^n lIDS a 12 &*j 
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ADVERTISING INDEX 



minimum ORDER; (1000 p*JS S3» shcfxig are! laming 

W-.i accept MC. V^j and Moixi/ Orden 

SEND ORDERS TO: Tin- ElKtrene CotRm 

p o ecu sue Scansdaie n ss»t 

PHONE ORDERS [S02) 151-71SJ FAX ORDERS ittKI 451-5MS 



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Electronics Now does not assume any responsibility for errors that may appear ir 
index below. 



Free Information Number 



Page 



108 AMC Sates K2 

75 Ace Products , 87 

107 All Electronics 105 

— Auiazing Concepts 1 04 

187 American Reliance Inc. 87 

195 Beckman Industrial 16, 17 

194 Beckman Industrial 2ft. 27 

98 Beckman Industrial CV4 

109 C & S Sales 33 

— CIE 11723 

185 Cable Warehouse 90 

— Cabletronics 102 

— Chenesko Products 87 

— Command Productions 83 

127 Deco Industries 87 

188 Electronic Goldmine 106 

— Electronics Book Club 7 

— Electronics Engineers B.C 28 

121 Fluke Manufacturing CV2 

— 47th Street Photo 34 

182 Global Specialties 3 

189 Goldstar Precision 15 

— Grantham College 59 

86 Heathkit 90 

— HighText Publications, lnc 17 

— ISCET 16 

114 Jameco 100. 101 

183 Kelvin 5 

178 Kcpco Power Supply 86 

176 Lake Sylvan Sales, lnc 106 

197 M&G Electronics 104 

87 MCM Electronics 99 

S3 MD Electronics 104 

93 Mark V, Electronics 98 

117 Mouser 86 

— NRI Schools 18 

71 NTE Electronics 23 



181 Northeast Electronics 

186 Number One Systems Ltd 

180 Optoelectronics C 

56 Parts Express . , 

184 People's College 

— R.E. Video Offer 

— Star Circuits 

179 TECI 

177 Tech Spray 

— The SPEC-COM Journal 

192 U.S. Cable 

190 Viejo Publications 

195 Xandi Electronics 

191 Zentek Corp 



ADVERTISING SALES OFFICI 
Gernsback Publications, Inc. 
5O0-B Bi-County Blvd. 
Farmingdale, NY 11735 
1-C516) 2833000 
President: Larry Stuck ler 
For Advertising ONLY 
516-293-3000 
Fax 1-516-293-3115 
Larry Stockier 

publisher 
Christina Estrada 

assistant to the President 
Arline Fishman 

advertising director 
Denise Mullen 

advertising assistant 
Kelly McQuade 

credit manager 
Subscriber Customer Service 
1- BOO- 2 8 8-0652 

Order Entry for New Subscribers 
I -800-993-71 39 
7:00 AM - 6:00 PMM-F MST 
ADVERTISING SALES OFFICES 
EAST/SOUTH EAST 
Stanley Levitan, Eastern Advertising £ 
Manager 
Electronics Now 
1 Overlook Ave. 
Great Neck, NY 11021 
1-516-487-9357, 1-516-293-3000 
Fax 1-516-487-B402 

MIDWEST/Texas/Arkansas/Okla, 

Ralph Bergen, Midwest Advertising Se 

Manager 

Electronics Now 

One Northfield Plaza, Suite 300 

Northfield, IL 60093-1214 

1-708-446-1444 

Fax 1-7OB-559-0562 

PACIFIC COAST/Mountain States 

Arline Fishman 

500-B Bi-County Blvd. 

Farmingdale, NY 11735 

1-CS16) 293-3000 

Fax 1-516-293-3115 

EN Shopper 

Joe Shore, National Representative 

P.O. Box 169 

Idyllwiid, CA 92549 

1-714-659-9743 

Fax 1-714-659-2469 



OPROTl 



LEMO 

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You want a 
bargraph & a full 
range counter - 
^Optoelectronics 
can deliver! 

Now for a limited time only, $160. 
off the list price, for our Full Range 
Model 2810 with bargraph - plus: 



•Full range -10Hz to 3GHz. 

• LCD display (daylight visibility). 

• True state-of-the-art technology 
with the high speed ASIC. 

NiCads & Charger included. 

• Ultra-high sensitivity. 

• 4 fast gate times. 

• Extruded metal case. 

• Compatible with MFJ207. 



Suggested options 

TA100S: 

Telescoping Whip Antenna $ 12. 

CC30 

Vinyl Carry Case $ 15. 

BUS: 

EL Backlight for use in roomlight and low 
light $ 45. 

TCXO 30: 

Precision ±0.2ppm 20 to 4Q°C temp, 
compensated time base $100. 



Made in 
the USA 





P^H 


1 ST*» 








— 



Universal 
Handi-Counter™ 
Model 3000, $375. and 
Bench Model 8030, $579. 
Both offer frequency, 
period, ratio and time 
interval. 



^ - ■ •> *T 



■ 



Call for free catalog - Factory Direct Order Line: 

I -R0O-3 2 7-59 1 

FL (305)771-2050 • FAX (305)771-2052 



5821 NE 14th Ave. • Ft. Lauderdale, FL 33334 
5% Ship/Handling (Max. $10) U.S. & Canada. 
15% outside continental U.S.A. 
Visa and Master Card accepted. 

CIRCLE 180 ON FREE INFORMATION CARD 



The DMM our 
customers 




Ttakth 



mectmt 



Caxaimx tfefer is 21 



Fmejusacy Gowtet to 2tftfi 



Exfeasfte Safety feafwes 



Before we built the new generation Beckman 
Industrial Series 2000 DMMs, we asked people 
like you what you really want. 

You want more. More test and measurement 
capabilities. More troubleshooting features. All 
in an affordable hand-held DMM. The Series 2000 
features the widest range Frequency Counter in 
any professional DMM, a full-range Capacitance 
Meter, True RMS measurements, Intermittent 
Detection, 50ns Pulse Detection, and Peak 
Measurement capabilities. Plus, the Series 2000 
is the only meter to offer autoranging Min/Max 
recording and relative modes. 

You want a DMM that's easier to use. The 
Series 2000's display is 25% larger, with bigger 
digits and backlighting for easier reading, even 
in the worst light. Plus the fast 4 digit display 
provides the high resolution needed for adjusting 
power supplies and generators down to lmV. 
And only the Series 2000 features a menuing 
system for fast, simple feature access. 




The Beckman Industrial Series 2000, pric 
from $209 to $279 offers you the best perfc 
mance for your dollar. Look again at these featu 

• 4 Digit, 10,000 Count Resolution 

• Basic Accuracy to 0.1% 

• True RMS, AC or AC on DC 

• 0.0112 Resolution 

• Automatic Reading Hold 

• 1ms Peak Hold 

• Fully Autoranging Relative and Min Max N 

• Intermittent Detector 

• UL1244, IEC1010 Design 

• Three Year Warranty 

The Series 2000 offers the most solutions for 
everyday test and measurement needs. The 
DMMs designed by the people who use them, 

For more information on these new DMMs 
call (outside CA) 1-800-854-2708 or 
(inside CA) 1-800-227-9781 . Beckman ML 
Industrial Corporation. 3883 Ruffin Rd.. AJ 
San Diego, CA 92123-1898. ^™ 



Beckman Industrial 7 

An Affiliate of Emerson Electric Co. 

' ' ' ■ 

CIRCLE 96 ON FREE INFORMATION CARD 



Spedtaitons subject 10 change witbi 
C 1992 Beckman Induarial Corp.